期刊
ADVANCED SCIENCE
卷 7, 期 5, 页码 -出版社
WILEY
DOI: 10.1002/advs.201902657
关键词
asymmetrical; dipole moment; energy loss; nonfullerene acceptors; organic solar cells
资金
- National Natural Science Foundation of China [21572171, 21702154, 51773157]
- Shenzhen Peacock Plan [KQTD20170330110107046]
- Shenzhen Technology and Innovation Commission [JCYJ20170413173814007, JCYJ20170818113905024]
- Research Grant Council of Hong Kong [14314216, T23-407/13-N]
Energy loss (E-loss) consisting of radiative recombination loss (Delta E-1 and Delta E-2) and nonradiative recombination loss (Delta E-3) is considered as an important factor for organic solar cells (OSCs). Herein, two N-functionalized asymmetrical small molecule acceptors (SMAs), namely N7IT and N8IT are designed and synthesized, to explore the effect of N on reducing E-loss with sulfur (S) as a comparison. N7IT-based OSCs achieve not only a higher PCE (13.8%), but also a much lower E-loss (0.57 eV) than those of the analogue (a-IT)-based OSCs (PCE of 11.5% and E-loss of 0.72 eV), which are mainly attributed to N7IT's significantly enhanced charge carrier density (promoting J(SC)) and largely suppressed nonradiative E-loss by over 0.1 eV (enhancing V-OC). In comparison, N8IT, with an extended pi-conjugated length, shows relatively lower photovoltaic performance than N7IT (but higher than a-IT) due to the less favorable morphology caused by the excessively large dipole moment of the asymmetrical molecule. Finally, this work sheds light on the structure-property relationship of the N-functionalization, particularly on its effects on reducing the E-loss, which could inspire the community to design and synthesize more N-functionalized SMAs.
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