| 1. |
- 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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| 2. |
- 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
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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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| 3. |
- 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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| 4. |
- Bandara, T M W J, 1968, et al.
(författare)
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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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| 5. |
- Bandara, T M W J, 1968, et al.
(författare)
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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
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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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| 6. |
- Bandara, T M W J, 1968, et al.
(författare)
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Performance enhancers for gel polymer electrolytes based on LiI and RbI for quasi-solid-state dye sensitized solar cells
- 2016
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:105, s. 103683-103691
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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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| 7. |
- Bandara, T M W J, 1968, et al.
(författare)
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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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