Journal
ADVANCED MATERIALS
Volume 34, Issue 27, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.202200361
Keywords
all-polymer solar cells; polymer acceptors; polymer conformation; organic solar cells; vinylene-linkers
Categories
Funding
- National Key Research and Development Program of China - MOST [2019YFA0705900]
- Basic and Applied Research Major Program of Guangdong Province [2019B030302007]
- National Natural Science Foundation of China (NSFC) [22075057]
- Shen Zhen Technology and Innovation Commission through (Shenzhen Fundamental Research Program) [JCYJ20200109140801751]
- Hong Kong Research Grants Council [C6023-19G, 16310019, 16310020, 16309221]
- Hong Kong Innovation and Technology Commission [ITC-CNERC14SC01]
- Foshan - HKUST [FSUST19-CAT0202]
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This study reports a high-performance polymer acceptor based on vinylene linkers, which exhibit a more coplanar and rigid molecular conformation compared to traditional thiophene-based acceptors. This leads to higher mobility and reduced energetic disorder. Furthermore, the blend based on this polymer acceptor demonstrates high domain purity, resulting in a better fill factor in all-polymer solar cells.
State-of-art Y-series polymer acceptors are typically based on a mono-thiophene linker, which can cause some twisted molecular conformations and thus limit the performance of all-polymer solar cells (all-PSCs). Here, a high-performance polymer acceptor based on vinylene linkers is reported, which leads to surprising changes in the polymers' molecular conformations, optoelectronic properties, and enhanced photovoltaic performance. It is found that the polymer acceptors based on thiophene or bithiophene linkers (PY-T-gamma and PY-2T-gamma) display significant molecular twisting between end-groups and linker units, while the vinylene-based polymer (PY-V-gamma) exhibits a more coplanar and rigid molecular conformation. As a result, PY-V-gamma demonstrates a better conjugation and tighter interchain stacking, which results in higher mobility and a reduced energetic disorder. Furthermore, detailed morphology investigations reveal that the PY-V-gamma-based blend exhibits high domain purity and thus a better fill factor in its all-PSCs. With these, a higher efficiency of 17.1% is achieved in PY-V-gamma-based all-PSCs, which is the highest efficiency reported for binary all-PSCs to date. This work demonstrates that the vinylene-linker is a superior unit to build polymer acceptors with more coplanar and rigid chain conformation, which is beneficial for polymer aggregation and efficient all-PSCs.
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