Journal
JOURNAL OF MATERIALS CHEMISTRY A
Volume 9, Issue 14, Pages 8975-8983Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/d1ta00838b
Keywords
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Funding
- National Key Research and Development Program of China - MOST [2019YFA0705900]
- Basic and Applied Basic Research Major Program of Guangdong Province [2019B030302007]
- Distinguished Young Scientists Program of Guangdong Province [2019B151502021]
- Natural Science Foundation of China [21875073, 21805099]
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This study designed a series of large-bandgap polymer donors and validated their device performances in all-polymer solar cells by combining them with a polymer acceptor, achieving high efficiency with a maximum of 15.8%. The systems showed more efficient charge transfer and less charge recombination as the energy-level offsets increased, leading to improved short-circuit current density, fill factors, and power conversion efficiency.
In this study, a series of large-bandgap polymer donors comprising dithieno[3 ',2 ':3,4;2 '',3 '':5,6]benzo[1,2-c][1,2,5]thiadiazole (fDTBT) and benzo[1,2-b:4,5-b ']dithiophene units with or without sulfur/fluorine substitution in the side-chains are designed. It is found that the energy levels of these polymer donors can be linearly tuned due to the pi-accepting properties of the sulfur atom and strong electron-withdrawing ability of the fluorine atom, while the absorption spectra keep nearly unchanged, which offers us the opportunity to balance the open-circuit voltage and charge separation driving force in all-polymer solar cells (all-PSCs). The device performances of these polymer donors are validated by combining them with the polymer acceptor PJ1. The device results indicate that as the energy-level offsets are increased, these systems exhibit a more efficient charge transfer and lesser charge recombination, which afford remarkably improved short-circuit current density, fill factors, and power conversion efficiency (PCE). Eventually, high-efficiency binary all-PSCs with a maximum efficiency of 15.8% are obtained, which is the highest value reported so far for all-PSCs. Moreover, this system demonstrates superior performance for 1 cm(2) all-PSC devices with a PCE of 14.4% and semitransparent all-PSC devices with a PCE of 10.3% (with average visible-light transmittance of 21.5%). Our study manifests that these fDTBT-based polymers are promising donor candidates for high-performance all-PSCs toward practical applications.
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