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Highly Efficient Indoor Organic Solar Cells by Voltage Loss Minimization through Fine-Tuning of Polymer Structures
journal contribution
posted on 2019-09-26, 14:08 authored by Ranbir Singh, Christos L. Chochos, Vasilis G. Gregoriou, Alkmini D. Nega, Min Kim, Manish Kumar, Sang-Chul Shin, Sang Hyeon Kim, Jae Won Shim, Jae-Joon LeeHerein,
we report a detailed study on the optoelectronic properties,
photovoltaic performance, structural conformation, morphology variation,
charge carrier mobility, and recombination dynamics in bulk heterojunction
solar cells comprising a series of donor–acceptor conjugated
polymers as electron donors based on benzodithiophene (BDT) and 5,8-bis(5-bromothiophen-2-yl)-6,7-difluoro-2,3-bis(3-(octyloxy)phenyl)quinoxaline
as a function of the BDT’s thienyl substitution (alkyl (WF3),
alkylthio (WF3S), and fluoro (WF3F)). The synergistic positive effects
of the fluorine substituents on the minimization of the bimolecular
recombination losses, the reduction of the series resistances (RS), the increment of the shunt resistances (RSh), the suppression of the trap-assisted recombination
losses, the balanced charge transport, the finer nanoscale morphology,
and the deeper highest occupied molecular orbital (EHOMO) are manifested versus the alkyl and alkylthio substituents.
According to these findings, the WF3F:[6,6]-phenyl-C71-butyric
acid methyl ester (PC71BM)-based organic photovoltaic device
is a rare example that features a high power conversion efficiency
(PCE) of 17.34% under 500 lx indoor light-emitting diode light source
with a high open-circuit voltage (VOC)
of 0.69 V, due to the suppression of the voltage losses, and a PCE
of 9.44% at 1 sun (100 mW/cm2) conditions, simultaneously.
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Keywords
recombination dynamicsBMWF 3SWF 3Fopen-circuit voltagemorphology variationseries resistancesoptoelectronic propertiescharge carrier mobilityvoltage lossespower conversion efficiencybulk heterojunctionPCEPC500 lxBDTalkylthio substituentstrap-assisted recombination lossesPolymer Structures Hereinshunt resistances0.69 Vphotovoltaic devicerecombination losseslight-emitting diode light sourcecharge transportWF 3F 71butyric acid methyl esternanoscale morphologyphotovoltaic performanceVoltage Loss Minimizationsuppressionelectron donorsOrganic Solar Cellsfluorine substituentsE HOMOV OC