| 1. |
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| 2. |
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| 3. |
- Albinsson, Ingvar, 1962, et al.
(författare)
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Intermediate temperature solid oxide fuel cells for solar energy systems
- 2005
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Ingår i: Proceedings of The 4th Sino-Swedish fuel cell workshop and joint Energy-Environment Forum. Ed. by . Zhu, B. , Mao, Z. , Mellander, B.-E. , Sundén, B. , Zhang, M.. ; , s. 69-
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Konferensbidrag (refereegranskat)
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| 4. |
- Albinsson, I., et al.
(författare)
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Ion association effects and ionic conduction in polyalkalene modified polydimethylsiloxanes
- 1992
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Ingår i: Solid State Ionics. - : Elsevier. - 0167-2738 .- 1872-7689. ; 53-56:Part 2, s. 1044-1053
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Tidskriftsartikel (refereegranskat)abstract
- Poly (ethylene oxide) and poly (propylene oxide) modified poly (dimethyl siloxane) (PDMS) have been complexed with LiCF3SO3, NaCF3SO3 and KCF3SO3. In order to study ion association in these systems, the nondegenerate symmetric stretch (A1, SO3) Raman modes have been studied as a function of temperature at several different salt concentrations. Ionic conductivity has also been measured. For the poly (ethylene oxide) modified PDMS (PEO-PDMS), ether oxygen to metal ratios ranged from 12500:1 to 9:1. Changing the cation from Li+ to Na+ to K+ increases the conductivity of the complex. Plots of the molar conductivity versus salt concentration show that the characteristic shape and the region of increase in the molar conductivity is influenced most by the fraction of “free” ions which increases with increasing salt concentration. Charged triplets and contact ion-pairs are also present at the higher salt concentrations; the number of triplets increases with concentration and temperature. Non-VTF behaviour is observed. For the poly (propylene oxide) modified PDMS (PPO-PDMS) (with excess PPO), phase separation is observed when these triflate salts are complexed in. These solutions above and below the boundary layer have been studied by Raman spectroscopy revealing that the upper region is siloxane rich. The formation of the boundary layer is attributed to an increasing difference in surface tension between the PPO/salt/PPO-PDMS complexes and the separate PPO, PPO-PDMS components. The boundary layer moves up with increase in salt concentration. There is evidence of “free” ions, contact-ion pairs, triplets and aggregates. Values of conductivity of 2.2×10−6 and 1.6×10−5 S/cm are quoted for 293 K and 8 mol% LiCF3SO3 in respectively PPO-PDMS/PPO and PEO-PDMS/PEO. Both are better conductors than the corresponding 8 mol% PPG4000/LiCF3SO3 complex.
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| 5. |
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| 6. |
- Althin, Rikard, et al.
(författare)
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Swedish employment offices: A new model for evaluating effectiveness
- 2010
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Ingår i: European Journal of Operational Research. - : Elsevier. - 0377-2217 .- 1872-6860. ; 207:3, s. 1535-1544
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Tidskriftsartikel (refereegranskat)abstract
- We measure how well Swedish employment offices perform in delivering the services required of them by the Swedish government. In contrast to earlier studies we use a dynamic efficiency framework, which allows us to better model the intertemporal nature of these services, explicitly allowing for placements of intermediate nature across periods. Rather than using second stage analysis to assess the effects of varying local labor market conditions and differences in client characteristics on performance, we include a measure of the office’s expected work load directly in the model. This measure, derived from duration analysis, is designed to capture the variation across offices in resources needed before an average individual can obtain employment. It is estimated from the characteristics of all unemployed individual and local labor market conditions.The empirical results demonstrate an increase in the office’s expected work loads over time and point to substantial differences in performance across offices. The results also point toward more than optimal placements in intermediate outputs such as non-matching jobs, training, and continued unemployment.
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| 7. |
- Amaraweera, Thng, et al.
(författare)
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Development of Li(Ni1/3Mn1/3Co1/3-x Na (x) )O-2 cathode materials by synthesizing with glycine nitrate combustion technique for Li-ion rechargeable batteries
- 2017
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Ingår i: Ionics. - : Springer Science and Business Media LLC. - 0947-7047 .- 1862-0760. ; 23:11, s. 3001-3011
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Tidskriftsartikel (refereegranskat)abstract
- Glycine nitrate combustion technique was investigated for synthesizing Li(Ni1/3Mn1/3Co1/3-x Na (x) )O-2, x = 0-0.11 based transition metal oxide cathode materials for the rechargeable Li-ion battery (LIB) under this study. X-ray diffraction and scanning electron microscopy analysis showed that the synthesized powder samples were well crystalline rather spherical secondary particles. These secondary particles were composed of softly agglomerated nano-scale primary particles. The room temperature electrical conductivity of these Na-doped materials was significantly higher than that of the base material (2.60 x 10(-7) S/cm). Among them, the x = 0.04 material reported the highest electrical conductivity of 1.02 x 10(-03) S cm(-1). The half-cell assembled with cathode fabricated from Li(Ni1/3Mn1/3Co1/3)O-2 base material showed an initial discharge capacity of 187 mA h(-1) g(-1) with 25 mA h(-1) g(-1) irreversible capacity loss and 88.47% columbic efficiency at C/5 rate with a cut-off voltage of 2.5-4.6 V at 25 A degrees C. The electrochemical behavior of the x = 0.04 cathode showed a comparable initial discharge capacity as of the base material but with improved capacity retention.
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| 8. |
- Amaraweera, T. H. N. G., et al.
(författare)
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Surface modification of natural vein graphite for the anode application in Li-ion rechargeable batteries
- 2018
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Ingår i: Ionics. - : Springer Science and Business Media LLC. - 0947-7047 .- 1862-0760. ; 24:11, s. 3423-3429
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Tidskriftsartikel (refereegranskat)abstract
- Natural vein graphite with high purity and crystallinity is seldom used as anode material in lithium-ion rechargeable batteries (LIB) due to impurities and inherent surface structure. This study focuses on improving the surface properties of purified natural vein graphite surface by employing mild chemical oxidation. Needle-platy graphite sample with initial average carbon percentage of 99.83% was improved to 99.98% after treatment with 5 vol.% HCl. Surface modification of purified graphite was done by chemical oxidation with (NH4)(2)S2O8 and HNO3. Fourier-transform infrared spectra of graphite after chemical indicating surface oxidation of graphite surface. X-ray diffraction and scanning electron microscopic studies show the improvement of graphite structure without modification of crystalline structure. Electrochemical performance of lithium-ion cell assembled with developed anode material shows noticeable improvement of the reversible capacity and coulombic efficiency in the first cycle and cycling behavior after surface modification.
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| 9. |
- Amaraweera, T. H. N. G., et al.
(författare)
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Synthesis of Li(Ni1/3Mn1/3Co1/3-xBax)O-2 cathode materials for lithium-ion rechargeable battery by glycine-nitrate combustion process
- 2019
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Ingår i: Ionics. - : Springer Science and Business Media LLC. - 0947-7047 .- 1862-0760. ; 25:6, s. 2501-2507
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Tidskriftsartikel (refereegranskat)abstract
- This study was based on developing Li(Ni1/3Mn1/3Co1/3-xBax)O-2 (x=0.04, 0.08, 0.11, 0.22, and 0.33) materials by substituting expensive Co with Ba, for the use in the cathode of rechargeable lithium-ion batteries (LIBs). Glycine-nitrate combustion method, which is a low-cost combustion technique, was employed to synthesize spherical shaped micron size secondary particles formed by densely agglomerated primary particles. The phase analysis performed by the X-ray diffractometry revealed the formation of the required layered phase of R-3m structure with trace amounts of a secondary phase. Furthermore, these Ba-substituted novel materials showed considerably higher electrical conductivity than those of the Li(Ni1/3Co1/3Mn1/3)O-2 base material. In the cell performance studies, the Ba-substituted cathode materials synthesized in this study showed slightly lower initial discharge capacity of 162.4mAhg(-1) but with considerably improved cycle performance compared to those of the Li(Ni1/3Co1/3Mn1/3)O-2 base material (187.7mAhg(-1)). More importantly, the Li(Ni1/3Mn1/3Co1/3-xBax)O-2, x=0.04 material clearly showed its ability to eliminate and prevent structural transformation usually associated with excess Li extraction at potentials above 4.5V. Therefore, the Li(Ni1/3Mn1/3Co1/3-xBax)O-2, x=0.04 material can be proposed as a potential candidate for the high-voltage cathode application of LIB.
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| 10. |
- Ambrosi, Aurelie, et al.
(författare)
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Development of heart block in children of SSA/SSB-autoantibody-positive women is associated with maternal age and displays a season-of-birth pattern
- 2012
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Ingår i: Annals of the Rheumatic Diseases. - London : BMJ Publishing Group. - 0003-4967 .- 1468-2060. ; 71:3, s. 334-340
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Tidskriftsartikel (refereegranskat)abstract
- Objective Congenital heart block may develop in the fetuses of Ro/SSA-positive and La/SSB-positive mothers. Recurrence rates of only 10-20% despite persisting maternal antibodies indicate that additional factors are critical for the establishment of heart block. The authors investigated the influence of other maternal and fetal factors on heart block development in a Swedish population-based cohort. less thanbrgreater than less thanbrgreater thanMethods The influence of fetal gender, maternal age, parity and time of birth on heart block development was analysed in 145 families, including Ro/La-positive (n=190) and Ro/La-negative (n=165) pregnancies. less thanbrgreater than less thanbrgreater thanResults There was a recurrence rate of 12.1% in Ro/La-positive women, and no recurrence in Ro/La-negative women. Fetal gender and parity did not influence the development of heart block in either group. Maternal age in Ro/La-positive pregnancies with a child affected by heart block was, however, significantly higher than in pregnancies resulting in babies without heart block (pandlt;0.05). Seasonal timing of pregnancy influenced the outcome. Gestational susceptibility weeks 18-24 occurring during January-March correlated with a higher proportion of children with heart block and lower vitamin D levels during the same period in a representative sample of Swedish women and a corresponding higher proportion of children with heart block born in the summer (pandlt;0.02). Maternal age or seasonal timing of pregnancy did not affect the outcome in Ro/La-negative pregnancies. less thanbrgreater than less thanbrgreater thanConclusion This study identifies maternal age and seasonal timing of pregnancy as novel risk factors for heart block development in children of Ro/La-positive women. These observations may be useful for counselling when pregnancy is considered.
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| 11. |
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| 12. |
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| 13. |
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| 14. |
- Anderson, Johan, 1973, et al.
(författare)
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Fire Spread due to Thermal Runaway in a Lithium-ion Battery Cell
- 2014
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Ingår i: Fires in vehicles (FIVE) 2014 Conference proceedings. ; 2014, s. 267-270
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The risk of spreading of fire between Lithium-ion battery cells is assessed using Finite-Element (FE) modelling of the heat transfer initiated by a thermal runaway. The results are contrasted to experimental data where the heat release rate (HRR) is utilized as an input to the simulation. It is found that the temperature increase in a neighbouring cell can be quantitatively estimated during theearly stages of the fire taking into account the anisotropic thermal conductivity of the cells.
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| 15. |
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| 16. |
- Anderson, Johan, 1973, et al.
(författare)
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Thermal modeling of fire propagation in lithium-ion batteries
- 2015
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Ingår i: The 24th International Technical Conference on the Enhanced Safety of Vehicles (ESV). Gothenburg, Sweden on June 8-11, 2015.
-
Konferensbidrag (refereegranskat)abstract
- The objective of the present work is to assess the risk of spreading of fire between Lithium-ion battery cellsinitiated by a thermal runaway. In particular it aims at developing means to predict the temperature of cells inthe vicinity of an overheated cell during the first 5-7 minutes after the thermal event in a Li-ion cell that has anorganic based electrolyte which is flammable. Finite-Element (FE) modelling is used to compute the heattransfer between cells. The spreading model is assessed modeling a scenario where the cells are exposed to a15 kW propane burner. Two different models where utilized, one that considers the conjugate heat transferbetween the surrounding hot gases and the battery cells while the second is a thermal model where theboundary conditions are measured in a mock-up test. The results from the two models are contrasted toexperimental data where the heat release rate (HRR) is utilized as an input to the simulation. It is found thatthe temperature increase in a neighboring cell can be quantitatively estimated in certain cases during the earlystages of the fire taking into account the anisotropic thermal conductivity of the cells using the conjugate heattransfer model. Moreover, the thermal model captures the qualitative behavior of the test results, however, thetemperature increase is slower in the computational model.
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| 17. |
- Andersson, Petra, et al.
(författare)
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Modelling of thermal events in Lithium-ion batteries
- 2015
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Ingår i: ESFSS 2015 2nd European Symposium on Fire Safety Science. 16 - 18 June 2015 European University Cyprus, Cyprus..
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Konferensbidrag (refereegranskat)abstract
- Lithium-ion batteries are seen as part of the solution to meet the environmental concerns for many areas including the automotive sector. The Li-ion technology has many good properties such as a high energy-density but also drawbacks such as its narrow window of stable operation. If the cell is e.g. heated up it might go into a thermal runaway in which the cell rapidly heats itself up, a process that might spread also to adjacent cells. In order to investigate whether a thermal event will progress to adjacent cells, it is important to be able to model the heat transport within a battery module properly. A first attempt to model the spreading has been made using Comsol Multiphysics for a test case where one cell is exposed to a heating source and then the heating spreads to other cells.
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| 18. |
- Arof, A. K., et al.
(författare)
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Polyacrylonitrile gel polymer electrolyte based dye sensitized solar cells for a prototype solar panel
- 2017
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 251, s. 223-234
-
Tidskriftsartikel (refereegranskat)abstract
- Polyacrylonitrile (PAN) based gel polymer electrolytes (GPE) were prepared using lithium iodide (LiI), 1-butyl-3-methylimidazolium iodide (BMII) and tetrapropyl ammonium iodide (TPAI). The LiI mass fraction in the electrolyte was varied while keeping the masses of other components constant in order to enhance the solar cell performance. The addition of 4.61 wt.% LiI in the GPE increased the electrolyte room temperature ionic conductivity from (2.32 ± 0.02) to (3.91 ± 0.04) mS cm−1. The increase in conductivity with the addition of LiI salts was attributed to the increase in diffusion coefficient, mobility and number density of charge carriers as determined from Nyquist plot fitting. The incorporation of LiI salts in PAN-based GPE has enhanced the efficiency of the DSSC as expected. The best cell performance was obtained with an electrolyte containing 4.61 wt.% LiI sandwiched between a single mesoporous layer of TiO2 soaked in N3 dye sensitizer and a platinum counter electrode, which showed a power conversion efficiency (PCE) of (5.4 ± 0.1) % with a short circuit current density (Jsc) of (21.0 ± 1.1) mA cm−2, an open circuit voltage (Voc) of (0.48 ± 0.02) V and a fill factor (FF) of (53.4 ± 0.9) %. The DSSCs with 4.61 wt.% of LiI have been used to fabricate prototype solar panels for operating small devices. The panels were assembled using a number of cells, each having an area of 2 cm × 2 cm, connected in series and parallel. The panel, consisting of a set of eight cells in series which was connected in parallel with another set of eight cells in series, produces an average power conversion efficiency of (3.7 ± 0.2)% with a maximum output power of (17.1 ± 0.9) mW. © 2017 Elsevier Ltd
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| 19. |
- Bandara, T M W J, 1968, et al.
(författare)
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A polymer electrolyte containing ionic liquid for possible applications in photoelectrochemical solar cells
- 2010
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Ingår i: Journal of Solid State Electrochemistry. - : Springer Science and Business Media LLC. - 1432-8488 .- 1433-0768. ; 14:7, s. 1221-1226
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Tidskriftsartikel (refereegranskat)abstract
- Various iodide ion conducting polymer electrolytes have been studied as candidate materials for fabricating photoelectrochemical (PEC) solar cells and energy storage devices. In this study, enhanced ionic conductivity values were obtained for the ionic liquid tetrahexylammonium iodide containing polyethylene oxide (PEO)-based plasticized electrolytes. The analysis of thermal properties revealed the existence of two phases in the electrolyte, and the conductivity measurements showed a marked conductivity enhancement during the melting of the plasticizer-rich phase of the electrolyte. Annealed electrolyte samples showed better conductivity than nonannealed samples, revealing the existence of hysteresis. The optimum conductivity was shown for the electrolytes with PEO:salt= 100:15 mass ratio, and this sample exhibited the minimum glass transition temperature of 72.2 °C. For this optimum PEO to salt ratio, the conductivity of nonannealed electrolyte was 4.4×10−4 S cm−1 and that of the annealed sample was 4.6×10−4 S cm−1 at 30 °C. An all solid PEC solar cell was fabricated using this annealed electrolyte. The short circuit current density (ISC), the open circuit voltage (VOC), and the power conversion efficiency of the cell are 0.63 mA cm−2, 0.76 V, and 0.47% under the irradiation of 600 W m−2 light.
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| 20. |
- Bandara, T M W J, 1968, et al.
(författare)
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Activated carbon synthesized from Jack wood biochar for high performing biomass derived composite double layer supercapacitors
- 2024
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Ingår i: CARBON TRENDS. - 2667-0569. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the electrochemical properties of bioderived activated carbon-based electrodes for supercapacitors formed using a sintered ceramic binder were investigated. Activated carbon derived from Jack wood tree (Artocarpus heterophyllus) with variable amounts of TiO2 nanoparticles as a binder, were used as electrodes in order to get good, activated carbon films on FTO substrates. No other binders were used in this study since most conventional binders devastate the electrical conductivity in the films. Furthermore, TiO2 has higher temperature tolerance compared to polymeric binders thus the electrode prepared can be used in wider applications. A series of electrochemical double-layer capacitors were fabricated and characterized by cyclic voltammetry and galvanostatic charge-discharge measurements. The supercapacitors prepared showed double-layer capacitive behavior. The electrodes that contain 90 % activated carbon and 10 % TiO2 show optimum performance along with an impressive specific capacitance of 147 F g-1 at 2 mV s-1 scan rate. This supercapacitor exhibits a power density of 68.5 W kg-1 while the energy density is 8.02 Wh kg-1. When the power density is as high as 1186.51 W kg-1 the energy density drops to 5.71 Wh kg-1. According to cyclic voltammetry measurements taken for 1000 cycles, the supercapacitor shows excellent cycle stability without any traces of capacitance drop.
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| 21. |
- Bandara, T M W J, 1968, et al.
(författare)
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Binary counter ion effects and dielectric behavior of iodide ion conducting gel-polymer electrolytes for high-efficiency quasi-solid-state solar cells
- 2020
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 22:22, s. 12532-12543
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Tidskriftsartikel (refereegranskat)abstract
- A series of highly efficient quasi-solid-state dye-sensitized solar cells (DSCs) is prepared by harnessing the binary cation effect and positive effects of the selected performance enhancers of gel-polymer electrolytes. The new electrolyte is composed of polyacrylonitrile polymer, tetra-hexylammonium iodide (Hex(4)NI) and KI binary salts as well as 4-tertbutylpyridine and 1-butyl-3-methylimidazolium iodide performance enhancers. The charge transport in the series of electrolytes is thermally activated and, accordingly, the temperature dependence of conductivity follows the VTF behavior. The enhancement of conductivity is observed with an increasing mass fraction of KI and decreasing mass fraction of Hex(4)NI, while the total mass fraction of salts in the electrolyte is kept unchanged. The highest conductivity of 3.74 mS cm(-1)at ambient temperature is shown by the sample containing KI only (without Hex(4)NI) at all the temperatures. The effects of dielectric polarization of the electrolytes are studied by analyzing the frequency dependence of the real and the imaginary parts of the AC conductivity in detail. Appropriate and reproducible cell construction are assured by efficiencies of above 5% exhibited by all the quasi-solid-state DSCs assembled using double-layered TiO(2)photo-electrodes and the new electrolyte series. Besides, highlighting the mixed cation effect, the cells with mixed salts exhibited efficiencies greater than 6%. An impressively high efficiency of 7.36% was shown by the DSC prepared with electrolyte containing 75 wt% KI and 25 wt% Hex(4)NI. This study reveals that the salt combination of KI and Hex(4)NI, which has not been reported before, is a suitable binary iodide salt mixture to prepare highly efficient DSCs. The replacement of tetra-hexylammonium ions by K(+)ions improves the charge transport in the electrolyte; however, the best solar cell performance is shown by the mixed salt system with 75 wt% KI and 25 wt% Hex(4)NI, which is not the highest conductivity composition. Therefore, the exhibited high efficiency of 7.36% is evidently due to the binary cation effect.
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| 22. |
- Bandara, T M W J, 1968, et al.
(författare)
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Characterization of poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) nanofiber membrane based quasi solid electrolytes and their application in a dye sensitized solar cell
- 2018
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 266, s. 276-283
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Tidskriftsartikel (refereegranskat)abstract
- The electrolyte plays a major role in dye sensitized solar cells (DSSCs). In this work a quasi-solid state (gel) electrolyte has been formed by incorporating a liquid electrolyte made with KI dissolved in ethylene carbonate (EC) and propylene carbonate (PC) co-solvent in poly (vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) co-polymer nanofiber membrane prepared by electrospinning. SEM images of the electrolyte membrane showed the formation of a three-dimensional network of polymer nanofibers with diameters between 100 and 300 nm and an average membrane thickness of 14 mu m. The electrolyte was characterized by FTIR and differential scanning calorimetry (DSC) measurements. The DSSCs fabricated with this electrolyte were characterized by current-voltage and Electrochemical Impedance Spectroscopy (EIS) measurements. DSC thermograms revealed that the crystallinity of the PVdF-HFP nanofiber is 14% lower than that of the pure PVdF-HFP polymer while the FTIR spectra showed a reduced polymer-polymer interaction in the nano fiber based gel electrolyte. The DSSCs fabricated with nanofiber based gel electrolyte showed an energy conversion efficiency of 5.36% under 1.5 a. m. solar irradiation, whereas the efficiency of the DSSC made with the liquid electrolyte based cell was 6.01%. This shows the possibility of replacing the liquid electrolyte in DSSCs by electro-spun polymer nanofiber based gel electrolyte and thereby minimizing some major drawbacks associated with liquid electrolyte based solar cells while maintaining a reasonably high efficiency.
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| 23. |
- Bandara, T M W J, 1968, et al.
(författare)
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Combined effect of alkaline cations and organic additives for iodide ion conducting gel polymer electrolytes to enhance efficiency in dye sensitized solar cells
- 2017
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 252, s. 208-214
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Tidskriftsartikel (refereegranskat)abstract
- Iodide ion conducting electrolytes are intensively studied as effectual electrolytes for dye-sensitized solar cells (DSSCs). However, the nature and concentration of the counter-ion (cation) in the electrolyte exert a profound influence on the performance of the thin film meso-porous TiO2 based DSSCs. A series of gel electrolytes containing the alkaline iodides LiI, NaI, KI, RbI and CsI and polyacrylonitrile (PAN) were fabricated together with the non-volatile plasticizers ethylene carbonate (EC) and propylene carbonate (PC). A similar series was fabricated with the inclusions of performance enhancers (additives) tetrapropylammonium iodide (Pr4NI), the ionic liquid 1-methyl-3-propyl imidazolium iodide (MPII) and 4-tert-butylpyridine (4TBP). The ionic conductivity of the electrolytes was studied in order to investigate its dependence on the nature of the alkaline cation in presence or absence of additives. The conductivities were higher for the electrolytes with the larger cations, namely K+, Rb+ and Cs+. A significant conductivity enhancement was observed in presence of the additives, and this effect was especially noticeable for samples with the smaller cations. The highest conductivity for electrolytes with additives, 3.96 mS cm(-1) at 25 degrees C, is exhibited by KI containing samples. (C) 2017 Elsevier Ltd. All rights reserved.
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| 24. |
- Bandara, T M W J, 1968, et al.
(författare)
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Conductivity behaviour in novel quasi-solid-state electrolyte based on polyacrylonitrile and tetrahexylammonium iodide intended for dye sensitized solar cells
- 2013
-
Ingår i: Journal of the National Science Foundation of Sri Lanka. - : Sri Lanka Journals Online (JOL). - 1391-4588 .- 2362-0161. ; 41:3, s. 175-184
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Tidskriftsartikel (refereegranskat)abstract
- The conduction of iodide ions in gel polymer electrolytes and the performance of dye sensitized solar cells containing such an electrolyte can be enhanced by incorporating a salt having a bulky cation. In this work, polyacrylonitrile (PAN) and Hex(4)N(+)I(-) based gel electrolytes with ethylene carbonate and propylene carbonate as plasticizers have been studied. The variation of conductivity and molar conductivity with salt concentration has been discussed in order to understand the mechanism of iodide ion conductivity in this system. Out of the various compositions studied, the electrolyte containing 120 % salt with respect to weight of PAN showed the highest conductivity, 2.0 X 10(-3) Scm(-1) at 25 degrees C and a glass transition at - 102.3 degrees C. The electrolytes exhibit predominantly ionic behaviour and because of the bulky cation a negligible cationic transport is shown. A quasi-solid-state dye sensitized solar cell was fabricated employing the optimized gel electrolyte. This cell showed an energy conversion efficiency of 3.1 % and a short circuit current density of 8.1 mAcm(-2) under irradiation of 1000 Wm(-2).
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| 25. |
- Bandara, T M W J, 1968, et al.
(författare)
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Dependence of solar cell performance on the nature of alkaline counterion in gel polymer electrolytes containing binary iodides
- 2017
-
Ingår i: Journal of Solid State Electrochemistry. - : Springer Science and Business Media LLC. - 1432-8488 .- 1433-0768. ; 21:6, s. 1571-1578
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Tidskriftsartikel (refereegranskat)abstract
- Performance of dye-sensitized nano-crystalline TiO2 thin film-based photo-electrochemical solar cells (PECSCs) containing gel polymer electrolytes is largely governed by the nature of the cation in the electrolyte. Dependence of the photovoltaic performance in these quasi-solid state PECSCs on the alkaline cation size has already been investigated for single cation iodide salt-based electrolytes. The present study reports the ionic conductivity dependence on the nature of alkaline cations (counterion) in a gel polymer electrolyte based on binary iodides. Polyacrylonitrile-based gel polymer electrolyte series containing binary iodide salts is prepared using one of the alkaline iodides (LiI, NaI, KI, RbI, and CsI) and tetrapropylammonium iodide (Pr4NI). All the electrolytes based on binary salts have shown conductivity enhancement compared to their single cation counterparts. When combined with Pr4NI, each of the Li+, Na+, K+, Rb+, and Cs+ cation containing iodide salts incorporated in the gel electrolytes has shown a room temperature conductivity enhancement of 85.59, 12.03, 12.71, 20.77, and 15.36%, respectively. The conductivities of gel electrolytes containing binary iodide systems with Pr4NI and KI/RbI/CsI are higher and have shown values of 3.28, 3.43, and 3.23 mS cm(-1), respectively at room temperature. The influence of the nature of counterions on the performance of quasi-solid state dye-sensitized solar cells is investigated by assembling two series of cells. All the binary cationic solar cells have shown more or less enhancements of open circuit voltage, short circuit current density, fill factor, and efficiency compared to their single cation counterparts. This work highlights the importance of employing binary cations (a large and a small) in electrolytes intended for quasi-solid state solar cells. The percentage of energy conversion efficiency enhancement shown for the PECSCs made with electrolytes containing Pr4NI along with Li+, Na+, K+, Rb+, and Cs+ iodides is 260.27, 133.65, 65.27, 25.32, and 8.36%, respectively. The highest efficiency of 4.93% is shown by the solar cell containing KI and Pr4NI. However, the highest enhancements of ionic conductivity as well as the energy conversion efficiency were exhibited by the PECSC made with Li+-containing binary cationic electrolyte.
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| 26. |
- Bandara, T M W J, 1968, et al.
(författare)
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Determination of charge carrier transport parameters in a polymer electrolyte intended for Li-ion batteries using electrochemical impedance analysis
- 2020
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Ingår i: Journal of Solid State Electrochemistry. - : Springer Science and Business Media LLC. - 1433-0768 .- 1432-8488. ; 24:5, s. 1207-1216
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Tidskriftsartikel (refereegranskat)abstract
- Solid polymer electrolytes are key components in many electrochemical devices. For an in-depth study of the basic parameters of such electrolytes, we developed a previously proposed method in order to determine the charge carrier density (n), mobility (μ), and diffusion coefficient (D) of ionic conductors using electrochemical impedance analysis. This reinforced method was tested with a composite solid electrolyte based on polyethylene oxide, ethylene carbonate, LiCF3SO3, and alumina filler by analyzing DC conductivity, frequency dependence of AC conductivity, and the complex dielectric function. The results show a clear picture of the temperature dependence of the parameters n, μ, and D; for example, at 20 °C, more than 15% of the total number of ions available in the electrolyte are mobile, and this value decreases with increasing temperature, most probably due to increased ion association in agreement with measurements using other techniques. The increase in ionic conductivity with increasing temperature is thus due to an increased mobility of the ionic species.
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| 27. |
- Bandara, T M W J, 1968, et al.
(författare)
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Diatom frustules enhancing the efficiency of gel polymer electrolyte based dye-sensitized solar cells with multilayer photoelectrodes
- 2020
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Ingår i: Nanoscale Advances. - : Royal Society of Chemistry (RSC). - 2516-0230. ; 2:1, s. 199-209
-
Tidskriftsartikel (refereegranskat)abstract
- The incorporation of nanostructures that improve light scattering and dye adsorption has been suggested for dye-sensitized solar cells (DSSCs), but the manufacture of photonic and nanostructured materials with the desired properties is not an easy task. In nature, however, the process of light-harvesting for photosynthesis has, in some cases, evolved structures with remarkable wavelength-sensitive light-trapping properties. The present work is focused on enhancing the efficiency of quasi solid-state DSSCs by capitalizing on the light trapping properties of diatom frustules since they provide complex 3-dimensional structures for scattering and trapping light. This study reports a promising approach to prepare TiO2 nanocrystal (14 nm) based photo-electrodes by utilizing the waveguiding and photon localization effects of nanostructured diatom frustules for enhancing light harvesting without deteriorating the electron conduction. Single and double-layered photo-electrodes were prepared with different frustule/nanocrystal combinations and conformations on transparent conductive oxide substrates. This study clearly reports impressive efficiency and short circuit current density enhancements of about 35% and 39%, respectively, due to the incorporation of diatom frustules extracted from a ubiquitous species. The SEM images obtained in this work reveal that the produced thin films had a remarkable surface coverage of evenly distributed frustules within the TiO2 nanoparticle layer. To the best of our knowledge, this study reports the first quasi solid-state DSSC based on a photo-electrode with incorporated bio-formed nanostructures.
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| 28. |
- Bandara, T M W J, 1968, et al.
(författare)
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Dye-sensitized, nano-porous TiO2 solar cell with poly(acrylonitrile): MgI2 plasticized electrolyte
- 2010
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 195:11, s. 3730-3734
-
Tidskriftsartikel (refereegranskat)abstract
- Dye-sensitized solar cells are promising candidates as supplementary power sources; the dominance in the photovoltaic field of inorganic solid-state junction devices is in fact now being challenged by the third generation of solar cells based on dye-sensitized, nano-porous photo-electrodes and polymer electrolytes. Polymer electrolytes are actually very favorable for photo-electrochemical solar cells and in this study poly(acrylonitrile)–MgI2 based complexes are used. As ambient temperature conductivity of poly(acrylonitrile)–salt complexes are in general low, a conductivity enhancement is attained by blending with the plasticizers ethylene carbonate and propylene carbonate. At 20 °C the optimum ionic conductivity of 1.9 × 10−3 S cm−1 is obtained for the (PAN)10(MgI2)n(I2)n/10(EC)20(PC)20 electrolyte where n = 1.5. The predominantly ionic nature of the electrolyte is seen from the DC polarization data. Differential scanning calorimetric thermograms of electrolyte samples with different MgI2 concentrations were studied and glass transition temperatures were determined. Further, in this study, a dye-sensitized solar cell structure was fabricated with the configuration Glass/FTO/TiO2/Dye/Electrolyte/Pt/FTO/Glass and an overall energy conversion efficiency of 2.5% was achieved under solar irradiation of 600 W m−2. The I–V characteristics curves revealed that the short-circuit current, open-circuit voltage and fill factor of the cell are 3.87 mA, 659 mV and 59.0%, respectively.
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| 29. |
- Bandara, T M W J, 1968, et al.
(författare)
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Dye sensitized solar cells with poly(acrylonitrile) based plasticized electrolyte containing Mgl(2)
- 2010
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 55:6, s. 2044-2047
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Tidskriftsartikel (refereegranskat)abstract
- Polymer electrolytes can be used favorably in photo-electrochemical solar cells. A possible electrolyte for this purpose is a polyacrylonitrile-Mgl(2) complex with plasticizers such as ethylene carbonate and propylene carbonate The best ionic conductivity was obtained for samples containing 60 wt% of Mgl(2) salt with respect to the weight of polyacrylonitrile, for example, at 30 degrees C the conductivity is 1.9 x 10(-3) S cm(-1) The ionic contribution to the conductivity is dominant as shown by do polarization tests. Furthermore, the glass transition temperature showed a minimum, -103.0 degrees C. for the sample with the highest conductivity indicating the importance of polymer chain flexibility for the conduction process Measurements on a fabricated solar cell with this electrolyte exhibited an overall energy conversion efficiency of 0.84%. The short circuit current density, open circuit voltage and fill factor of the cell were 2 04 mA cm(-2), 692 mV and 59.3%, respectively.
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| 30. |
- Bandara, T M W J, 1968, et al.
(författare)
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Effect of cation size on the performance of dye sensitized nanocrystalline TiO2 solar cells based on quasi-solid state PAN electrolytes containing quaternary ammonium iodides
- 2013
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 109, s. 609-616
-
Tidskriftsartikel (refereegranskat)abstract
- The performance of dye sensitized nanocrystalline TiO2 solar cells based on quasi-solid state PAN electrolytes containing a series of six quaternary ammonium iodide salts NH4I, Eth(4)NI, Prop(4)NI, But(4)NI, Pent(4)NI, Hex(4)NI with different cation sizes has been evaluated. Even though the total ionic conductivity decreases with increasing cation size from NH4I to Hex(4)NI, the iodide ion conductivity in the electrolytes increases with cation size. The open circuit photovoltage (V-oc) of the dye sensitized solar cells also increases with cation radius. The efficiency of the DSSCs varies with cation size and exhibits a maximum for Prop(4)NI salt. The short circuit photo current density (J(sc)) follows a similar variation with cation size, suggesting a strong correlation between the cation size dependence of efficiency and J(sc). The DSSC fabricated with tetrapropylammonium iodide exhibited the maximum efficiency of 4.30% with maximum J(sc) of 10.78 mA cm(-2) and a V-oc of 0.746 V. The results have been interpreted on the basis of "the electrolyte effects" where J(sc) is determined essentially by the iodide ion conductivity and "the electrode effects" where the J(sc) and V-oc are determined by the cation adsorption in the dyed TiO2 electrode and resulting electron dynamics at the semiconductor/electrolyte interface. For DSSCs with small cations, electrolyte effects appear to be dominating and rate determining while for DSSCs with larger cations, electrode effects appear to be dominating and rate determining. (C) 2013 Elsevier Ltd. All rights reserved.
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| 31. |
- Bandara, T M W J, 1968, et al.
(författare)
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Effect of the alkaline cation size on the conductivity in gel polymer electrolytes and their influence on photo electrochemical solar cells
- 2016
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 18:16, s. 10873-10881
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Tidskriftsartikel (refereegranskat)abstract
- The nature and concentration of cationic species in the electrolyte exert a profound influence on the efficiency of nanocrystalline dye-sensitized solar cells (DSSCs). A series of DSSCs based on gel electrolytes containing five alkali iodide salts (LiI, NaI, KI, RbI and CsI) and polyacrylonitrile with plasticizers were fabricated and studied, in order to investigate the dependence of solar cell performance on the cation size. The ionic conductivity of electrolytes with relatively large cations, K+, Rb+ and Cs+, was higher and essentially constant, while for the electrolytes containing the two smaller cations, Na+ and Li+, the conductivity values were lower. The temperature dependence of conductivity in this series appears to follow the Vogel-Tamman-Fulcher equation. The sample containing the smallest cation shows the lowest conductivity and the highest activation energy of similar to 36.5 meV, while K+, Rb+ and Cs+ containing samples show an activation energy of similar to 30.5 meV. DSSCs based on the gel electrolyte and a TiO2 double layer with the N719 dye exhibited an enhancement in the open circuit voltage with increasing cation size. This can be attributed to the decrease in the recombination rate of electrons and to the conduction band shift resulting from cation adsorption by TiO2. The maximum efficiency value, 3.48%, was obtained for the CsI containing cell. The efficiencies shown in this study are lower compared to values reported in the literature, and this can be attributed to the use of a single salt and the absence of other additives, since the focus of the present study was to analyze the cation effect. The highest short circuit current density of 9.43 mA cm(-2) was shown by the RbI containing cell. The enhancement of the solar cell performance with increasing size of the cation is discussed in terms of the effect of the cations on the TiO2 anode and ion transport in the electrolyte. In liquid electrolyte based DSSCs, the short circuit current density has been reported to decrease with the increasing size of the cation. However, in this work, it follows an opposite trend highlighting a major difference between liquid and quasi-solid electrolytes on the solar cell performance.
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| 32. |
- Bandara, T M W J, 1968, et al.
(författare)
-
Effect of thermal history and characterization of plasticized, composite polymer electrolyte based on PEO and tetrapropylammonium iodide salt (Pr4N+I-).
- 2009
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 180:4-5, s. 362-
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Tidskriftsartikel (refereegranskat)abstract
- The search for anionic conductors based on solid polymer electrolytes is important for the development of photo-electrochemical (PEC) solar cells due to their many favourable chemical and physical properties. Although solid polymer electrolytes have been extensively studied as cation, mainly lithium ion, conductors for applications in secondary batteries, their use as anionic conductors have not been studied in greater detail. In a previous paper we reported the application of a PEO based iodide ion conducting electrolyte in a PEC solar cell. This electrolyte had the composition PEO: Pr4N+I- = 9:1 with 50 wt.% ethylene carbonate (EC). In this work we have studied the effect of incorporating alumina filler on the properties of this electrolyte. The investigation was extended to electrical and dielectric measurements including high frequency impedance spectroscopy and thermal analysis.In the DSC themograms two endothermic peaks have been observed on heating, one of these peaks is attributed with the melting of the PEO crystallites, while the other peak with a melting temperature similar to 30 degrees C is attributed to the melting of the EC rich phase. The melting temperature of both these peaks shows a marked variation with alumina content in the electrolyte. The temperature dependence of the conductivity shows that there is an abrupt conductivity increase in the first heating run evidently due to the melting of the EC rich phase. High conductivity values are retained at lower temperatures in the second heating. Conductivity isotherms show the existence of two maxima, one at -5% Al2O3 content and the other at similar to 15%. The occurrence of these two maxima has been explained in terms of the interactions caused by alumina grains, the crystallinity and melting of the PEO rich phase. As seen from latent heat of melting, the crystallinity of the electrolyte has reduced considerably during the first heating run. In contrast to the conductivity enhancement caused by ceramic fillers in PEO-based cation containing electrolytes, no conductivity enhancement has been observed in the present PEO based anionic conducting materials by adding alumina except at low temperatures. (C) 2009 Elsevier B.V. All rights reserved.
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| 33. |
- Bandara, T M W J, 1968, et al.
(författare)
-
Efficiency enhancement in dye sensitized solar cells using gel polymer electrolytes based on a tetrahexylammonium iodide and MgI2 binary iodide system
- 2012
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 14:24, s. 8620-8627
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Tidskriftsartikel (refereegranskat)abstract
- Quasi-solid-state dye-sensitized solar cells have drawn the attention of scientists and technologists as a potential candidate to supplement future energy needs. The conduction of iodide ions in quasi-solid-state polymer electrolytes and the performance of dye sensitized solar cells containing such electrolytes can be enhanced by incorporating iodides having appropriate cations. Gel-type electrolytes, based on PAN host polymers and mixture of salts tetrahexylammonium iodide (Hex(4)N(+)I(-)) and MgI2, were prepared by incorporating ethylene carbonate and propylene carbonate as plasticizers. The salt composition in the binary mixture was varied in order to optimize the performance of solar cells. The electrolyte containing 120% Hex(4)N(+)I(-) with respect to weight of PAN and without MgI2 showed the highest conductivity out of the compositions studied, 2.5 x 10(-3) S cm(-1) at 25 degrees C, and a glass transition at -102.4 degrees C. However, the electrolyte containing 100% Hex(4)N(+)I(-) and 20% MgI2 showed the best solar cell performance highlighting the influence of the cation on the performance of the cell. The predominantly ionic behaviour of the electrolytes was established from the dc polarization data and all the electrolytes exhibit iodide ion transport. Seven different solar cells were fabricated employing different electrolyte compositions. The best cell using the electrolyte with 100% Hex(4)N(+)I(-) and 20% MgI2 with respect to PAN weight showed 3.5% energy conversion efficiency and 8.6 mA cm(-2) short circuit current density.
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| 34. |
- Bandara, T M W J, 1968, et al.
(författare)
-
Efficiency enhancement in dye-sensitized solar cells with a novel PAN-based gel polymer electrolyte with ternary iodides
- 2015
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Ingår i: Journal of Solid State Electrochemistry. - : Springer Science and Business Media LLC. - 1433-0768 .- 1432-8488. ; 19:8, s. 2353-2359
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Tidskriftsartikel (refereegranskat)abstract
- The dye-sensitized solar cells (DSSCs) are promising, but their efficiency and stability require improvements. Quasi-solid-state DSSCs, based on gel polymer electrolytes, have exhibited reasonable performance with binary iodides. In this work, polyacrylonitrile-based gel polymer electrolytes were prepared using three iodide salts namely lithium iodide (LiI), 1-butyl-3-methylimidazolium iodide (BMII), and tetrapropyl ammonium iodide (Pr4NI) and investigated for their suitability for improving the performance of DSSCs. Hence, the LiI content was optimized for enhancement of both conductivity and DSSC performance employing fixed amounts of Pr4NI and BMII, and the compositions investigated had the chemical formula (PAN)(10)(EC)(25)(PC)(20)(BMII) (Pr4NI)(0.75)(LiI)(n)(I-2)(n/10). The highest room temperature ionic conductivity, 3.93 mS cm(-1), was obtained for the electrolyte sample with LiI molar fraction n = 1.75, out of the prepared set of electrolytes. This electrolyte in a DSSC with a single mesoporous layer of TiO2 produced the best efficiency of 5.41 % with J (sc) of 20.6 mA cm(-2). The changes in short circuit current density, open circuit voltage, and cell efficiency with the composition of the electrolyte are explained considering possible influences of cations in the electrolytes toward the electron injection from dye to TiO2, the electron diffusion through TiO2, shift of flat band potentials, and conductivity in the electrolyte. The incorporation of LiI into the electrolyte with the binary iodide system enhanced the efficiency by 30 % and the J (sc) by 62 % in the DSSCs fabricated with such electrolytes. This work uncovers the advantage of using ternary iodides in quasi-solid-state DSSCs rather than single or binary iodides.
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| 35. |
- Bandara, T M W J, 1968, et al.
(författare)
-
Efficiency enhancement of dye-sensitized solar cells with PAN:CsI:LiI quasi-solid state (gel) electrolytes
- 2014
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Ingår i: Journal of Applied Electrochemistry. - : Springer Science and Business Media LLC. - 1572-8838 .- 0021-891X. ; 44:8, s. 917-926
-
Tidskriftsartikel (refereegranskat)abstract
- While many attempts have been made in the recent past to improve the power conversion efficiencies of dye-sensitized solar cells (DSSCs), only a few reports can be found on the study of these cells using binary iodides in the gel polymer electrolyte. This paper reports the effect of using a binary mixture of (large and small cation) alkaline salts, in particular CsI and LiI, on the efficiency enhancement in DSSCs with gel polymer electrolytes. The electrolyte with the binary mixture of CsI:LiI = 1:1 (by weight) shows the highest ionic conductivity 2.9 x 10(-3) S cm(-1) at 25 A degrees C. DC polarization measurements showed predominantly ionic behavior of the electrolyte. The density of charge carriers and mobility of mobile ions were calculated using a newly developed method. The temperature dependent behavior of the conductivity can be understood as due to an increase of both the density and mobility of charge carriers. The solar cell with only CsI as the iodide salt gave an energy conversion efficiency of similar to 3.9 % while it was similar to 3.6 % for the cell with only LiI. However, the electrolyte containing LiI:CsI with mass ratio 1:1 showed the highest solar cell performance with an energy conversion efficiency of similar to 4.8 % under the irradiation of one Sun highlighting the influence of the mixed cation on the performance of the cell. This is an efficiency enhancement of 23 %.
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| 36. |
- Bandara, T M W J, 1968, et al.
(författare)
-
Efficiency of 10 % for quasi-solid state dye-sensitized solar cells under low light irradiance
- 2015
-
Ingår i: Journal of Applied Electrochemistry. - : Springer Science and Business Media LLC. - 0021-891X .- 1572-8838. ; 45:4, s. 289-298
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Tidskriftsartikel (refereegranskat)abstract
- Polyacrylonitrile-based gel electrolytes were prepared using tetrapropylammonium iodide salt for dye-sensitized solar cells (DSSCs). The optimized gel electrolyte exhibited an ionic conductivity of 2.6 mS cm(-1) at 25 A degrees C and the DSSC fabricated with this gel electrolyte showed open-circuit voltage, short-circuit current density, fill factor, and efficiency of 0.71 V, 11.8 mA, 51, and 4.2 %, respectively, under one sun irradiation. The efficiency of the cell increases increased with decreasing solar irradiance achieving 10 % efficiency and 80 % fill factor at 3 mW cm(-2) a low irradiance value of 3 mW cm(-2). Lower efficiencies at higher intensities were attributed to transport limitation of the redox mediators at high irradiation intensities. This work suggests that quasi-solid state DSSCs can reach efficiencies close to that of liquid electrolyte-based cells at low irradiance levels. The results open up new vistas on efficiency improvement in DSSCs by optical manipulation and control of DSSCs.
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| 37. |
- Bandara, T M W J, 1968, et al.
(författare)
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Electrical and complex dielectric behaviour of composite polymer electrolyte based on PEO, alumina and tetrapropylammonium iodide
- 2017
-
Ingår i: Ionics. - : Springer Science and Business Media LLC. - 0947-7047 .- 1862-0760. ; 23:7, s. 1711-1719
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the electrical, dielectric and morphological analysis of composite solid polymer electrolytes containing polyethylene oxide, alumina nano-fillers and tetrapropylammonium iodide are conducted. The temperature dependence of conductivity shows activation energy of 0.23, 0.20 and 0.29 eV for electrolytes containing 0, 5 and 15 wt.% alumina, respectively, when data fitted to the Arrhenius equation. These activation energy values are in good agreement with those determined from dielectric measurements. The result confirms the fact that conductivity is activated by both the mobility and the charge carrier density. The conductivity isotherms demonstrated the existence of two peaks, at 5 and 15 wt.% Al2O3 composition. The highest conductivity values of 2.4 × 10−4, 3.3 × 10−4 and 4.2 × 10−4 S cm−1 are obtained for the sample with 5 wt.% Al2O3 at 0, 12 and 24 °C, respectively, suggesting an enhancement of conductivity compared with that of alumina free samples.
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| 38. |
- Bandara, T M W J, 1968, et al.
(författare)
-
High efficiency dye-sensitized solar cell based on a novel gel polymer electrolyte containing RbI and tetrahexylammonium iodide (Hex(4)NI) salts and multi-layered photoelectrodes of TiO2 nanoparticles
- 2019
-
Ingår i: Renewable & Sustainable Energy Reviews. - : Elsevier BV. - 1364-0321 .- 1879-0690. ; 103, s. 282-290
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Tidskriftsartikel (refereegranskat)abstract
- High efficiency dye sensitized solar cells (DSSCs) have been achieved using a novel polymer gel electrolyte containing RbI and tetrahexylammonium iodide (Hex(4)NI) binary salts in combination with multi-layered TiO2 photoelectrodes. Performance enhancers were incorporated to the electrolyte to improve the efficiency in the DSSCs. Varying the salt mass fraction, showed that the conductivity in the electrolyte increases with increasing amount of RbI. The highest ionic conductivity of 4.19 mS cm(-1) is exhibited by the electrolyte sample with RbI: Hex(4)NI weight ratio of 3:1 at 25 degrees C. The temperature dependence of the electrolytes shows Arrhenius behavior. It is found that the electrolyte with RbI: Hex(4)NI weight ratio of 1.06:1 is more suitable for DSSC's applications and it has a conductivity of 3.77 mS cm(-1). A colloidal suspension of P25 TiO2 nanoparticles was used to make the spin coated photo-anodes in the form of stacks of 1-6 layers. The formation of a highly uniform and porous structure is observed with increasing number of layers from scanning electron microscopy and X-ray diffraction studies revealed that the layers are predominantly anatase phase with crystallite size of 19-22 nm. The band gap was estimated to be around 3.22 eV based on UV-Visible spectroscopy and found to be decreasing slightly with increasing layer thickness. The maximum efficiency of 7.5% and an impressively high current density of 20 mA cm(-2) were observed for the 4-layer device with the new gel electrolyte based on RbI and Hex(4)NI. This study not only brings reliability and consistency to the ways of preparing well-ordered TiO2 photoanodes but also offers the possibility of low-cost practical and highly efficient quasi-solid state DSSCs.
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| 39. |
- Bandara, T M W J, 1968, et al.
(författare)
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Mobile charge carrier concentration and mobility of a polymer electrolyte containing PEO and Pr4N+I- using electrical and dielectric measurements
- 2011
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 189:1, s. 63-68
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Tidskriftsartikel (refereegranskat)abstract
- For the characterization and development of new electrolytes it is important to know the number of free charge carriers and their mobility. A new method has been developed to estimate the charge carrier density, n, and mobility, mu, for an electrolyte using dielectric measurements and a space charge relaxation model. In order to verify the applicability of this method, it has been tested with an aqueous KI solution electrolyte. The method was then applied to a polyethylene oxide (PEO) based polymer electrolyte. In the case of the polymer electrolyte, plasticized and non plasticized electrolytes intended for photo-electrochemical solar cells containing Pr4N+I- salt which is an iodide ion conductor at room temperature was used. The significant conductivity increase that occurs during the PEO crystallite melting is shown to be due to a large and abrupt increase of the concentration of mobile charge carriers. It is also shown that, for the PEO above the crystallite melting temperature, the introduction of the plasticizer results in an increased mobility. Results from the solution electrolyte show good agreement with known values.
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| 40. |
- Bandara, T M W J, 1968, et al.
(författare)
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N719 and N3 dyes for quasi-solid state dye sensitized solar cells - A comparative study using polyacrylonitrile and CsI based electrolytes
- 2016
-
Ingår i: Ceylon Journal of Science. - : Sri Lanka Journals Online (JOL). - 2513-230X .- 2513-2814. ; 45:2, s. 61-69
-
Tidskriftsartikel (refereegranskat)abstract
- Dye sensitized solar cells offer a low cost alternative technology for solar energy harvesting. However, there are long term stability issues connected with these cells due to the liquid electrolytes normally used. Gel or solid polymer electrolytes which do not contain volatile solvents have been used in this investigation in order to alleviate these problems. Two types of solar cells were assembled using a double layered TiO2 film sensitized with two types of dye sensitizers, namely N719 (Ruthenizer 535-bisTBA) and N3 (Ruthenizer 535) in order to compare their performance. Quasi-solid-state electrolytes based on PAN (polyacrylonitrile) as the host polymer and CsI as the iodide salt were prepared by incorporating ethylene carbonate (EC) and propylene carbonate (PC) as plasticizers. The conductivity of the electrolyte was further improved by adding tetrapropylammonium iodide (Pr4NI), 1-methyl 3-propyl imidazolium iodide (MPII) and 4-tert-butylpyridine (4TBP). The incorporation of these additives resulted in 17% enhancement in ionic conductivity. This improved electrolyte was used to fabricate the solar cells with N3 and N719 dyes. The efficiency of the N3 dye based solar cell was 3.85% whereas the efficiency of the N719 dye based solar cell was 4.14% representing a significant efficiency enhancement by 7.53% by the N719 dye. In addition, due to additives the solar cell efficiency has enhanced by 19% compared to the solar cell without any additive.
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| 41. |
- Bandara, T M W J, 1968, et al.
(författare)
-
Novel photo-voltaic device based on Bi_{1−x}La_xFeO_3 perovskite films with higher efficiency
- 2019
-
Ingår i: Journal of Materials Science: Materials in Electronics. - : Springer Science and Business Media LLC. - 1573-482X .- 0957-4522. ; 30:2, s. 1654-1662
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Tidskriftsartikel (refereegranskat)abstract
- Photovoltaic cells using polycrystalline La substituted bismuth iron oxide, Bi1−xLaxFeO3, (0.1 ≤ x ≤ 0.4), films as the light harvesting component were investigated in this work. A novel cell set-up utilizing a double layered TiO2 film as top contact and a thin layer of quasi-solid polymer electrolyte as back contact was used and a significant enhancement in cell efficiency was observed for assemblies based on x ≥ 0.2 samples, coincident with a structural transition of Bi1−xLaxFeO3 from ferroelectric to non-ferroelectric. The power conversion efficiency of the PV device was 0.13% for the cell with x = 0.2 at 1 sun irradiation. The short circuit current density for this La composition was 0.35 mA cm−2. A hysteretic behaviour was observed for higher La compositions when the scanning is from open-circuit (OP) to short-circuit (SC) which may be attributed to polarization effects. The results at x ≥ 0.2 show an improved performance with respect to BiFeO3 based systems, suggesting the stabilization of the non-ferroelectric crystal structure leads either to a more efficient separation of photo-generated electron–hole pairs and/or enhanced charge transport. The findings represent a step towards the realisation of facile to fabricate, inorganic solid state photovoltaic devices.
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| 42. |
- Bandara, T M W J, 1968, et al.
(författare)
-
Performance enhancers for gel polymer electrolytes based on LiI and RbI for quasi-solid-state dye sensitized solar cells
- 2016
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:105, s. 103683-103691
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the effect of additives (enhancers) on efficiency enhancement in dye sensitized solar cells (DSSCs) containing two series of gel polymer electrolytes, one based on LiI and the other based on RbI have been systematically studied. Polyacrylonitrile (PAN) was used as the host polymer while the performance enhancers used in each case were tetrapropylammoniumiodide (Pr4NI), the ionic liquid 1-methyl-3-propyl imidazolium iodide (MPII) and 4-tert-butylpyridine (4TBP) respectively. Appropriate amounts of the selected enhancers were incorporated one by one, in LiI based and RbI based gel electrolytes. The incorporation of Pr4NI and MPII led to an increase in conductivity of the electrolyte, while 4TBP showed a decrease in conductivity. The maximum conductivity of 3.85 mS cm(-1) at room temperature was shown by the RbI based-series while for the LiI based series the maximum conductivity was 2.95 mS cm(-1). Each of these electrolytes with respective additives was used to fabricate quasi-solid state DSSCs. For the DSSCs based on the LiI containing series, a significant short circuit current density (J(sc)) enhancement (161%) from 3.65 to 9.54 mA cm(-2) was observed due to the addition of Pr4NI. This J(sc) value further increased to 9.7 mA cm(-2) due to the addition of MPII and 4TBP. For the DSSCs with corresponding Rb based electrolytes with all three additives, the highest J(sc) value obtained was 11.5 mA cm(-2). The incorporation of the three additives Pr4NI, MPII and 4TBP collectively enhanced the open circuit voltages and the efficiencies of both LiI and RbI containing quasi-solid state DSSCs. Another important finding from this work is that rarely used RbI containing electrolytes exhibit superior DSSC performance compared to more frequently used LiI based electrolytes. Hence, RbI appears to be a better candidate compared to LiI to fabricate gel polymer electrolytes for DSSCs in general. The three additives have contributed to a remarkable efficiency enchantment in DSSCs by 449.3% for the LiI based electrolyte and by 35.7% for the RbI based electrolyte.
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| 43. |
- Bandara, T M W J, 1968, et al.
(författare)
-
Polyethyleneoxide (PEO)-based, anion conducting solid polymer electrolyte for PEC solar cells
- 2008
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Ingår i: Journal of Solid State Electrochemistry. - : Springer Science and Business Media LLC. - 1433-0768 .- 1432-8488. ; 12:7-8, s. 913-917
-
Konferensbidrag (refereegranskat)abstract
- Solid polymer electrolyte membranes were prepared by complexing tetrapropylammoniumiodide (Pr4N+I-) salt with polyethylene oxide (PEO) plasticized with ethylene carbonate (EC), and these were used in photoelectrochemical (PEC) solar cells fabricated with the configuration glass/FTO/TiO2/dye/electrolyte/Pt/FTO/glass. The PEO/Pr4N+I-+I-2=9:1 ratio gave the best room temperature conductivity for the electrolyte. For this composition, the plasticizer EC was added to increase the conductivity, and a further conductivity enhancement of four orders of magnitude was observed. An abrupt increase in conductivity occurs around 60-70 wt% EC; the room temperature conductivity was 5.4 x 10(-7) S cm(-1) for 60 wt% EC and 4.9 x 10(-5) S cm(-1) for the 70 wt% EC. For solar cells with electrolytes containing PEO/Pr4N+I-+I-2=9:1 and EC, IV curves and photocurrent action spectra were obtained. The photocurrent also increased with increasing amounts of EC, up to three orders of magnitude. However, the energy conversion efficiency of this cell was rather low.
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| 44. |
- Bandara, T M W J, 1968, et al.
(författare)
-
Quasi solid state polymer electrolyte with binary iodide salts for photo-electrochemical solar cells
- 2014
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 39:6, s. 2997-3004
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Tidskriftsartikel (refereegranskat)abstract
- Quasi-solid-state polymer electrolytes can be used in dye sensitized solar cells (DSSCs) in order to overcome various problems associated with liquid electrolytes. Prior to fabricating commercially viable solar cells, the efficiency of quasi solid state DSSCs needs to be improved. Using electrolytes with a binary iodide mixture is a novel technique used to obtain such efficiency enhancement. In this work we report both conductivity and solar cell performance enhancements due to incorporation of a mixture containing LiI and tetrahexylammonium iodide in a quasi-solid-state electrolyte. The conductivity of the electrolyte increases with added amounts of Lit and thus the highest conductivity, 3.15 x 10(-3) S cm(-2) at 25 degrees C, is obtained for the electrolyte 100 wt% LiI. The predominantly ionic behavior of the electrolytes was established from dc polarization measurements. The iodide ion conductivity, measured using iodine pellet electrodes decreased somewhat with increasing amount of LiI even though the overall conductivity increased. However, the highest efficiency was obtained for the DSSC containing a polymer electrolyte with Hex(4)N(+)I:LiI = 1:2 mass ratio. This cell had the largest short circuit current density of about 13 mA cm(-2) and more than 4% overall energy conversion efficiency. The results thus show that electrolytes with Hex(4)N(+)I/LiI mixed iodide system show better DSSC performance than single iodide systems. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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| 45. |
- Bandara, T M W J, 1968, et al.
(författare)
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Tetrahexylammonium iodide containing solid and gel polymer electrolytes for dye sensitized solar cells
- 2012
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 14, s. 1607-1612
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Konferensbidrag (refereegranskat)abstract
- The performance evaluation plays a more and more important role in the modern enterprise management, and the method of evaluation system on enterprise performance is always an important question in the theory and practice. So this paper set up a scientific, reasonable performance evaluation index system which was especially suitable for the small and medium third party logistics enterprise from the four levels of financial, customers, business and innovation. Meanwhile, according to the index system, it gave a performance evaluation with the Chinese access logistics corporation. The results showed that the construction of the index system was reasonable, and the evaluation results also were reliable.
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| 46. |
- Bandara, T M W J, 1968, et al.
(författare)
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Thermal and dielectric properties of PEO/EC/Pr4N+I- polymer electrolytes for possible applications in photo-electro chemical solar cells.
- 2009
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Ingår i: Journal of Solid State Electrochemistry. - : Springer Science and Business Media LLC. - 1432-8488 .- 1433-0768. ; 13:8
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Tidskriftsartikel (refereegranskat)abstract
- The anion-conducting polymer electrolyte polyethylene oxide (PEO)/ethylene carbonate (EC)/Pr4N+I-/I-2 is a candidate material for fabricating photo-electrochemical (PEC) solar cells. Relatively high ionic conductivity values are obtained for the plasticized electrolytes; at room temperature, the conductivity increases from 7.6 x 10(-9) to 9.5 x 10(-5) S cm(-1) when the amount of EC plasticizer increases from 0% to 50% by weight. An abrupt conductivity enhancement occurs at the melting of the polymer; above the melting temperature, the conductivity can reach values of the order of 10(-3) S cm(-1). The melting temperature decreases from 66.1 to 45.1 A degrees C when the EC mass fraction is increased from 0% to 50%, and there is a corresponding reduction in the glass transition temperature from -57.6 to -70.9 A degrees C with the incorporation of the plasticizer. The static dielectric constant values, epsilon(s), increase with the mass fraction of plasticizer, from 3.3 for the unplasticized sample to 17.5 for the 50% EC sample. The dielectric results show only small traces of ion-pair relaxations, indicating that the amount of ion association is low. Thus, the iodide ion is well dissociated, and despite its large size and relatively low concentration in these samples, the iodide ion to ether oxygen ratio is 1:68, a relatively efficient charge carrier. A further enhancement of the ionic conductivity, especially at lower temperatures, is however desired for these applications.
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| 47. |
- Bandara, T M W J, 1968, et al.
(författare)
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Transport parameters of charge carriers in PEO-LiTf-based, plasticized, composite, and plasticized-composite electrolytes intended for Li-ion batteries
- 2022
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Ingår i: Ionics. - : Springer Science and Business Media LLC. - 0947-7047 .- 1862-0760. ; 28:6, s. 2701-2714
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Tidskriftsartikel (refereegranskat)abstract
- Solid polymer electrolytes are a key component in many electrochemical devices such as dye-sensitized solar cells, batteries, and supercapacitors. In this study, three electrolytes based on polyethylene oxide (PEO) host polymer, ethylene carbonate (EC) plasticizer, and Al2O3 filler were investigated. The polymer electrolytes (PEO)9(EC)9(LiCF3SO3)2, (PEO)9(LiCF3SO3)2(Al2O3)0.75, and (PEO)9(EC)9(LiCF3SO3)2(Al2O3)0.75 were characterized by analyzing DC conductivity, the frequency dependence of AC conductivity, and complex dielectric function. The conductivities of the plasticized, composite, and plasticized-composite electrolytes at 26 °C increase from 6.25, 0.009, and 2.96 mS cm-1 to 21.5, 0.12, and 11.4 mS cm-1, respectively, when the temperature increased to 70 °C. For the in-depth analysis of electrolytes, dielectric analysis was used to determine the charge carrier density (n), mobility (μ), and diffusion coefficient (D) using a newly developed method. Further, the investigation extended to study the temperature dependence of n, D, and μ. The study reveals that EC can increase the ionic conductivity by increasing n, and conversely, filler contributes by increasing μ, respectively. At 26 °C, (PEO)9(EC)9(LiCF3SO3)2(Al2O3)0.75 shows D, μ, and n of 3.8×10-11 m2 s-1, 1.5×10-9 m2 V-1 s-1, and 1.3×1027 m-3, respectively. The values obtained for D, μ, and n parameters of the plasticized electrolytes agree with those available for similar electrolytes, while the composite electrolyte showed considerably lower values for n. The complex impedance analysis can be used to determine transport parameters of all the types (plasticized, composite, and plasticized composite) of polymer electrolytes.
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| 48. |
- Bennmarker, Helge, et al.
(författare)
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Do regional payroll tax reductions boost employment?
- 2009
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Ingår i: Labour Economics. - : Elsevier BV. - 0927-5371 .- 1879-1034. ; 16:5, s. 480-489
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Tidskriftsartikel (refereegranskat)abstract
- Using a Difference-in-Differences approach, we evaluate the effects of a 10 percentage point reduction in the payroll tax introduced in 2002 in northern Sweden. We find no employment effects among firms existing both before and after the reform, whereas the average wage bill per employee increases by about 0.25% per percentage point reduction in the tax rate. Extending the analysis to include entry and exit of firms, we find evidence of positive effects on the number of firms and a tendency to positive employment effects. Moreover, the wage incidence estimates become insignificant when we account for entry and exit of firms.
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| 49. |
- Bertilsson, S., et al.
(författare)
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Lithium-ion battery electrolyte emissions analyzed by coupled thermogravimetric/Fourier-transform infrared spectroscopy
- 2017
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 365, s. 446-455
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Tidskriftsartikel (refereegranskat)abstract
- In the last few years the use of Li-ion batteries has increased rapidly, powering small as well as large applications, from electronic devices to power storage facilities. The Li-ion battery has, however, several safety issues regarding occasional overheating and subsequent thermal runaway. During such episodes, gas emissions from the electrolyte are of special concern because of their toxicity, flammability and the risk for gas explosion. In this work, the emissions from heated typical electrolyte components as well as from commonly used electrolytes are characterized using FT-IR spectroscopy and FT-IR coupled with thermogravimetric (TG) analysis, when heating up to 650 degrees C. The study includes the solvents EC, PC, DEC, DMC and EA in various single, binary and ternary mixtures with and without the LiPF6 salt, a commercially available electrolyte, (LP71), containing EC, DEC, DMC and LiPF6 as well as extracted electrolyte from a commercial 6.8 Ah Li-ion cell. Upon thermal heating, emissions of organic compounds and of the toxic decomposition products hydrogen fluoride (HF) and phosphoryl fluoride (POF3) were detected. The electrolyte and its components have also been extensively analyzed by means of infrared spectroscopy for identification purposes.
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| 50. |
- Bettucci, Ottavia, et al.
(författare)
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Organic dye-sensitized solar cells containing alkaline iodide-based gel polymer electrolytes: Influence of cation size
- 2018
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 20:2, s. 1276-1285
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Tidskriftsartikel (refereegranskat)abstract
- The electrolyte used in dye-sensitized solar cells (DSSCs) plays a key role in the process of current generation, and hence the analysis of charge-transfer mechanisms both in its bulk and at its interfaces with other materials is of fundamental importance. Because of solvent confinement, gel polymer electrolytes are more practical and convenient to use with respect to liquid electrolytes, but in-depth studies are still necessary to optimize their performances. In this work, gel polymer electrolytes of general formulation polyacrylonitrile (PAN)/ethylene carbonate (EC)/propylene carbonate (PC)/MI, where M + is a cation in the alkaline series Li-Cs, were prepared and used in DSSCs. Their ionic conductivities were determined by impedance analysis, and their temperature dependence showed Arrhenius behavior within the experimental window. FT-IR studies of the electrolytes confirmed the prevalence of EC coordination around the cations. Photo-anodes were prepared by adsorbing organic sensitizer D35 on nanocrystalline TiO 2 thin films, and employed to build DSSCs with the gel electrolytes. Nanosecond transient spectroscopy results indicated a slightly faster dye regeneration process in the presence of large cations (Cs + , Rb + ). Moreover, a negative shift of TiO 2 flat-band potential with the decreasing charge density of the cations (increasing size) was observed through Mott-Schottky analysis. In general, results indicate that cell efficiencies are mostly governed by photocurrent values, in turn depending on the conductivity increase with cation size. Accordingly, the best result was obtained with the Cs + -containing cell, although in this case a slight reduction of photovoltage compared to Rb + was observed.
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