Enhanced intermolecular interactions to improve twisted polymer photovoltaic performance
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In polymer solar cells (PSCs), twisted polymer donors usually have low photovoltaic efficiencies due to their poor photoactive layer morphologies. Herein, we successfully improved twisted polymer (PBDT-3T) photovoltaic efficiency by employing C=O groups (PBDT-3TCO) to enhance intermolecular interactions. The maximum power conversion efficiency (PCE) of PBDT-3T is only 1.05%, while the PCE of PBDT-3TCO reaches 11.77% in non-fullerene (NF) PSCs. Both polymers-based PSCs show very similar open-circuit voltages but remarkable differences in their short-circuit currents and fill factors. The single crystals of both functionalized terthiophenes with methyl substituents demonstrate that the terthiophene with C=O units changes molecular pattern by forming intra/inter molecular S...O and O...H interactions but its molecular planarity does not significantly improve. Our comparative studies show that PBDT-3TCO with C=O units possesses a strong aggregation property and optimal photoactive layer morphology in NF PSCs. This study provides important insight into the design of high-performance twisted polymer donors for NF PSCs.
Keywordstwisted polymer donors carbonyl group intermolecular interaction polymer solar cells
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This work was supported by the National Natural Science Foundation of China (51703228, 21835006, 21504066), the Chinese Academy of Sciences (XDB12030200), and the Ministry of Science and Technology (2016YFA0200700). X-ray data was acquired at beamlines 7.3.3 and 18.104.22.168 at the Advanced Light Source, which is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The authors thank Chenhui Zhu at beamline 7.3.3, and Cheng Wang at beamline 22.214.171.124 for assistance with data acquisition.
- 48.Wu Y, Wang Z, Meng X, Ma W. Prog Chem, 2017, 29: 93–101Google Scholar