期刊
SMALL METHODS
卷 6, 期 4, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/smtd.202200007
关键词
aggregation behaviors; molecular design; non-fused ring acceptors; single crystal structures; transfer integral calculations
资金
- National Key Research and Development Program of China [2019YFE0116700]
- National Natural Science Foundation of China [21835006, 22075017]
Stable and planar molecular geometry is achieved in non-fused electron acceptors A4T-25 and A4T-26 by introducing bulk side groups. The compact pi-pi stacking in A4T-26 promotes efficient charge transportation, resulting in higher electron mobility. When blended with the same polymer donor, the photovoltaic cell based on A4T-26 shows an enhanced power conversion efficiency compared to A4T-25.
To obtain stable and planar molecular geometry in non-fused electron acceptors, A4T-25 and A4T-26 are designed and synthesized by introducing the bulk 2,4,6-triisopropylphenyl side groups onto different positions of the central two thiophene units. A4T-25 and A4T-26 both show a narrow-bandgap of 1.39 and 1.46 eV, with highest occupied molecular orbital/lowest unoccupied molecular orbital levels of -5.56/-3.81 and -5.65/-3.83 eV, respectively, and the electrostatic potential distributions imply that they have strong electron-accepting capability. The single crystal structure analysis and the transfer integral calculation demonstrate that the much more compact pi-pi stacking in A4T-26 can promote efficient charge transportation compared to that in A4T-25. Therefore, the electron mobility of A4T-26 is obviously higher and more balanced than that of A4T-25. When blending the two acceptors with the same polymer donor PBDB-TF, the photovoltaic cell based on PBDB-TF:A4T-25 has an inadequate power conversion efficiency (PCE) of 7.83%, while the PBDB-TF:A4T-26-based one yields an enhanced PCE of 12.1%. Overall, this study offers an insight into the relationship between the fine-tuning of the molecular structure of non-fused ring acceptors and the corresponding charge transfer process in organic solar cells.
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