摘要
Nonfused ring electron acceptors(NFREAs)are promising candidates for future commercialization of organic solar cells(OSCs)due to their simple synthesis.Still,the power conversion efficiencies(PCEs)of NFREA-based OSCs have large room for improvement.In this work,by merging end group halogenation and side chain engineering,we developed four A-D-A’-D-A type NFREAs,which we refer to as EH-4F,C4-4F,EH-4Cl,and C4-4Cl.Single crystal X-ray diffraction revealed that multiple intermolecular S⋅⋅⋅F interactions between cyclopentadithiophene and 5,6-difluoro-3-(dicyanomethylene)indanone could cause an unfavorable dimer formation,leading to ineffectiveπ-πstackings in EH-4F and C4-4F,whereas no such dimer was found in EH-4Cl and C4-4Cl after replacing with 5,6-dichloro-3-(dicyanomethylene)indanone.Moreover,although the shorter n-butyl side chain resulted in a closer molecular packing in C4-4Cl,EH-4Cl(2-ethylhexyl substitution)with proper crystallinity exhibited enhanced face-on orientation in thin film,which is favorable for vertical charge transport and further reducing charge recombination.As a result,a PCE of 13.0%is obtained for EH-4Cl-based OSC with a fill factor of 0.70.This work highlights the importance of molecular packing and orientation control toward future high-performance A-D-A’-D-A type NFREAs.
基金
National Key Research and Development Program,Grant/Award Number:2019YFA0705900
National Natural Science Foundation of China,Grant/Award Numbers:22275058,U20A6002,22109046
Guangdong Basic and Applied Basic Research Foundation,Grant/Award Numbers:2022B1515120008,2022A1515011417
Guangdong Innovative and Entrepreneurial Research Team Program,Grant/Award Number:2019ZT08L075。
