Journal
ADVANCED MATERIALS
Volume 34, Issue 5, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.202106316
Keywords
all-small-molecule solar cells; miscibility; ordered molecular packing; organic solar cells; phase separation
Categories
Funding
- National Natural Science Foundation of China [51973044, 21721002, 51961135103]
- Youth Innovation Promotion Association, Chinese Academy of Sciences
- Strategic Priority Research Program of Chinese Academy of Sciences [XDB36000000]
- Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy [DE-AC02-05CH11231]
- ONR [N000142012155]
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This study proposes a strategy to alleviate the conflict between small domain and ordered packing in ASM-OSCs by modulating molecular interactions to achieve good miscibility and packing simultaneously. The optimized morphology with multi-length-scale domains and highly ordered packing resulted in a record efficiency of 16.2% in ASM-OSCs, demonstrating the effectiveness of this approach in designing high-performance organic solar cells.
In all-small-molecule organic solar cells (ASM-OSCs), a high short-circuit current (J(sc)) usually needs a small phase separation, while a high fill factor (FF) is generally realized in a highly ordered packing system. However, small domain and ordered packing always conflicted each other in ASM-OSCs, leading to a mutually restricted J(sc) and FF. In this study, alleviation of the previous dilemma by the strategy of obtaining simultaneous good miscibility and ordered packing through modulating homo- and heteromolecular interactions is proposed. By moving the alkyl-thiolation side chains from the para- to the meta-position in the small-molecule donor, the surface tension and molecular planarity are synchronously enhanced, resulting in compatible properties of good miscibility with acceptor BTP-eC9 and strong self-assembly ability. As a result, an optimized morphology with multi-length-scale domains and highly ordered packing is realized. The device exhibits a long carrier lifetime (39.8 mu s) and fast charge collection (15.5 ns). A record efficiency of 16.2% with a high FF of 75.6% and a J(sc) of 25.4 mA cm(-2) in the ASM-OSCs is obtained. These results demonstrate that the strategy of simultaneously obtaining good miscibility with high crystallinity could be an efficient photovoltaic material design principle for high-performance ASM-OSCs.
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