Journal
CHEMISTRY OF MATERIALS
Volume 31, Issue 19, Pages 8044-8051Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.chemmater.9b02501
Keywords
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Funding
- National Natural Science Foundation of China [51603100, 51773087, 21733005]
- Shenzhen Fundamental Research program [KQJSCX20180319114442157, JCYJ20170817111214740]
- Shenzhen Nobel Prize Scientists Laboratory Project [C17783101]
- Guangdong Innovative and Entrepreneurial Research Team Program [2016ZT06G587]
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Brominated A-D-A-type small-molecule acceptor ITIC-2Br-gamma with certain molecular structure was designed and synthesized. Compared to the mixture of three isomers (ITIC-2Br-m), ITIC-2Br-gamma shows stronger absorption in the region of 600-800 nm, which is beneficial to afford higher J(SC). Furthermore, single-crystal structure analysis of ITIC-2Br-gamma indicates that although the bromine atom has a larger size, the end groups of adjacent molecules still exhibit strong interactions with short pi-pi distance of 3.28 angstrom. Because of the Br center dot center dot center dot S and O center dot center dot center dot S interactions, all molecules form an interpenetrated three-dimensional network, which is beneficial for the charge to transport along multidirections. The organic solar cells (OSCs) based on the PBDB-T-2F:ITIC-2Br-gamma blend film exhibit a higher power conversion efficiency (PCE) of 12.05% due to its better film morphology and higher charge mobilities, whereas a PBDB-T-2F:ITIC-2Br-m-based device only shows a moderate PCE of 10.88%. These results indicate that separation and purification of the brominated A-D-A-type small molecules are an effective way to further improve their photovoltaic performances. Furthermore, bromination is easily synthesized and is of low-cost, which exhibits great potential for the preparation of large-scale OSCs.
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