| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Lin, Yuze, et al.
(författare)
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Mapping Polymer Donors toward High-Efficiency Fullerene Free Organic Solar Cells
- 2017
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 29:3
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Tidskriftsartikel (refereegranskat)abstract
- Five polymer donors with distinct chemical structures and different electronic properties are surveyed in a planar and narrow-bandgap fused-ring electron acceptor (IDIC)-based organic solar cells, which exhibit power conversion efficiencies of up to 11%.
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| 3. |
- Peng, Zuosheng, et al.
(författare)
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One-step coating inverted polymer solar cells using a conjugated polymer as an electron extraction additive
- 2015
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Ingår i: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 3:41, s. 20500-20507
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Tidskriftsartikel (refereegranskat)abstract
- We report a facile technique of blending a conjugated polymer thieno[3,4-b]thiophene/benzodithiophene (PTB7):[6,6]-phenyl-C71-butyric acid methyl ester (PCBM[70]) active materials with a conjugated interfacial modification polymer poly[(9,9-bis(3-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) to simplify the coating process and improve the bulk heterojunction (BHJ) polymer solar cell (PSC) performance. The reason for and result of PFN self-organization via a spontaneous vertical delamination onto the ITO surface were investigated by charge transfer state, optical modelling based on transfer matrix formalism, surface energy measurement, scanning Kelvin probe force microscopy and impedance spectroscopy analysis in conjunction with atomic force microscopy and scanning electron microscopy. The relaxed charge transfer state demonstrates that PFN doping has a negligible impact on the donor: acceptor heterojunction interface. The optical simulation of device structures indicates that doping PFN into a BHJ has nearly no influence on the photon absorption profile of the active layer. Very encouraging device performance was achieved in the one-step coating PFN: BHJ PSC with ITO as the cathode, which is comparable to that of the two-step coating PSC. Moreover, for ITO-free inverted PSCs with PEDOT:PSS as the incident light top-electrode, decent device performance can also be obtained, demonstrating the remarkable universality through this facile strategy.
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| 4. |
- Bakulin, Artem A., et al.
(författare)
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Morphology, Temperature, and Field Dependence Separation in High-Efficiency Solar Cells Based on Polyquinoxaline Copolymer
- 2016
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 120:8, s. 4219-4226
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Tidskriftsartikel (refereegranskat)abstract
- Charge separation and recombination are key processes determining the performance of organic optoelectronic devices. Here we combine photoluminescence and photovoltaic characterization of organic solar cell devices with ultrafast multipulse photocurrent spectroscopy to investigate charge generation mechanisms in the organic photovoltaic devices based on a blend of an alternating polyquinoxaline copolymer with fullerene. The combined use of these techniques enables the determination of the contributions of geminate and bimolecular processes to the solar cell performance. We observe that charge separation is not a temperature-activated process in the studied materials. At the same time, the generation of free charges shows a dear external field and morphology dependence. This indicates that the critical step of charge separation involves the nonequilibrium state that is formed at early times after photoexcitation, when the polaronic localization is not yet complete. This work reveals new aspects of molecular level charge dynamics in the organic light-conversion systems.
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| 5. |
- Bao, Qinye, et al.
(författare)
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Effects of ultraviolet soaking on surface electronic structures of solution processed ZnO nanoparticle films in polymer solar cells
- 2014
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488. ; 2:41, s. 17676-17682
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Tidskriftsartikel (refereegranskat)abstract
- We systematically show the effect of UV-light soaking on surface electronic structures and chemical states of solution processed ZnO nanoparticle (ZnONP) films in UHV, dry air and UV-ozone. UV exposure in UHV induces a slight decrease in work function and surface-desorption of chemisorbed oxygen, whereas UV exposure in the presence of oxygen causes an increase in work function due to oxygen atom vacancy filling in the ZnO matrix. We demonstrate that UV-light soaking in combination with vacuum or oxygen can tune the work function of the ZnONP films over a range exceeding 1 eV. Based on photovoltaic performance and diode measurements, we conclude that the oxygen atom vacancy filling occurs mainly at the surface of the ZnONP films and that the films consequently retain their n-type behavior despite a significant increase in the measured work function.
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| 6. |
- Elfwing, Anders, et al.
(författare)
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DNA Based Hybrid Material for Interface Engineering in Polymer Solar Cells
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 10:11, s. 9579-9586
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Tidskriftsartikel (refereegranskat)abstract
- A new solution processable electron transport material (ETM) is introduced for use in photovoltaic devices, which consists of a metallic conjugated polyelectrolyte, poly(4-(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl-methoxy)-1-butanesulfonic acid (PEDOT-S), and surfactant-functionalized deoxyribonucleic acid (DNA) (named DNA:CTMA:PEDOT-S). This ETM is demonstrated to effectively work for bulk-heterojunction organic photovoltaic devices (OPV) based on different electron acceptor materials. The fill factor, the open circuit voltage, and the overall power conversion efficiency of the solar cells with a DNA:CTMA:PEDOT-S modified cathode are comparable to those of devices with a traditional lithium fluoride/aluminum cathode. The new electron transport layer has high optical transmittance, desired work function and selective electron transport. A dipole effect induced by the use of the surfactant cetyltrimethylammonium chloride (CTMA) is responsible for lowering the electrode work function. The DNA:CTMA complex works as an optical absorption dilutor, while PEDOT-S provides the conducting pathway for electron transport, and allows thicker layer to be used, enabling printing. This materials design opens a new pathway to harness and optimize the electronic and optical properties of printable interface materials.
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| 7. |
- Fan, Qunping, 1989, et al.
(författare)
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Over 14% efficiency all-polymer solar cells enabled by a low bandgap polymer acceptor with low energy loss and efficient charge separation
- 2020
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry. - 1754-5692 .- 1754-5706. ; 13:12, s. 5017-5027
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Tidskriftsartikel (refereegranskat)abstract
- Obtaining both high open-circuit voltage (V-oc) and short-circuit current density (J(sc)) has been a major challenge for efficient all-polymer solar cells (all-PSCs). Herein, we developed a polymer acceptor PF5-Y5 with excellent optical absorption capability (onset extending to similar to 880 nm and maximum absorption coefficient exceeding 105 cm(-1) in a film), high electron mobility (3.18 x 10(3) cm(2) V-1 s(-1)) and high LUMO level (-3.84 eV) to address such a challenge. As a result, the PBDB-T:PF5-Y5-based all-PSCs achieved a high power conversion efficiency of up to 14.45% with both a high Voc (0.946 V) and a high Jsc (20.65 mA cm(-2)), due to the high and broad absorption coverage, small energy loss (0.57 eV) and efficient charge separation and transport in the device, which are among the best values in the all-PSC field. In addition, the all-PSC shows a similar to 15% improvement in PCE compared to its counterpart small molecule acceptor (Y5)-based device. Our results suggest that PF5-Y5 is a very promising polymer acceptor candidate for applications in efficient all-PSCs.
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| 8. |
- Gao, Feng, et al.
(författare)
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The Effect of Processing Additives on Energetic Disorder in Highly Efficient Organic Photovoltaics : A Case Study on PBDTTT-C-T:PC71BM
- 2015
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Ingår i: Advanced Materials. - : Wiley-VCH Verlag. - 0935-9648 .- 1521-4095. ; 27:26, s. 3868-3873
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Tidskriftsartikel (refereegranskat)abstract
- Energetic disorder, an important parameter affecting the performance of organic photovoltaics, is significantly decreased upon the addition of processing additives in a highly efficient benzodithiophene-based copolymer blend (PBDTTT-C-T:PC71BM). Wide-angle and small-angle X-ray scattering measurements suggest that the origin of this reduced energetic disorder is due to increased aggregation and a larger average fullerene domain size together with purer phases.
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| 9. |
- Gedefaw, Desta, et al.
(författare)
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Design, Synthesis and Computational Study of Fluorinated Quinoxaline-Oligothiophene-based Conjugated Polymers with Broad Spectral Coverage
- 2018
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Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 19:24, s. 3393-3400
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Tidskriftsartikel (refereegranskat)abstract
- Donor-acceptor (D-A) copolymers typically show two absorption peaks in the visible region, flanking a valley region of limited absorptivity. One strategy for more panchromatic light harvesting is to incorporate side-groups orthogonal to the polymer backbone, which enable 2D pi conjugation and can give rise to additional absorption peaks. Here we design and synthesize two D-A polymers which both carry a fluorinated quinoxaline acceptor unit, but while P1 includes a benzodithiophene donor moiety with thiophene side-groups (2D-BDT), the P2 polymer lacks 2D conjugation in its simpler pentathiophene donor segment. The P1 polymer consequently shows an atypical absorption profile with more panchromatic absorption with no apparent valley in the spectrum. In order to understand the structure-electronic relations, the optical and electrochemical properties were predicted using a previously developed computational approach. The predicted optical properties show very good agreement with the experimental results. Solar cells made from P1 show a short-circuit current more than twice as large as P2, attributed to its enhanced spectral coverage. However, poor fill factors limit the preliminary power conversion efficiencies to 3.3 % for P1 and 1.0 % for P2 as blended with PCBM[70] in a 1 : 1.5 (w/w) ratio.
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| 10. |
- George, Zandra, 1985, et al.
(författare)
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Two-in-one : Cathode modification and improved solar cell blend stability through addition of modified fullerenes
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:7, s. 2663-2669
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of dual purpose modified fullerenes with pyridine-as well as amine-functional groups is reported. Addition of these fullerenes to a polymer : fullerene bulk-heterojunction blend based on a thiophene-quinoxaline donor polymer is found to modify the active layer/cathode interface of inverted solar cells (glass/ITO/active layer/MoO3/Al). In particular the open-circuit voltage of devices is increased from 0.1 V to about 0.7 V, which results in a drastic rise in photovoltaic performance with a power conversion efficiency of up to 3%. At the same time, presence of the functionalised fullerene additives prevents the detrimental formation of micrometre-sized fullerene crystals upon annealing at 140 degrees C. As a result, the device performance is retained, which promises significantly increased thermal stability of the bulk-heterojunction blend nanostructure.
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