Competition between singlet fission and singlet exciton dissociation at the interface in TIPS-pentacene:IT-4F blend

Abstract

Abstract The competition between singlet fission and exciton dissociation is important for the fabrication of singlet fission organic solar cell (SF-OSC) with bulk heterojunction structure (BHJ). Possible multiple pathways, such as the dissociation of singlet, triplet exciton and triplet pair intermediate (1(TT)) into charges, must be taken into account in SF-OSC due to tremendous interface between donor and acceptor. Here, we systematically investigate the photo-physical processes in 6,13-Bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) and 3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6,7-difluoro)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d’]-s-indaceno[1,2-b:5,6-b’]dithiophene (IT-4F) blend by the steady-state and transient optical spectroscopy. Although the crystallinity of TIPS-pentacene is poor in BHJ film, the disappearance of long-lived component in the triplet exciton rise time is suggestive of rapid singlet fission rate. Evident long lifetime of BHJ film in triplet exciton decay curve might be attributed to dissociation of 1(TT) into charges and recombination or triplet exciton traps, both of which suggest the singlet fission outcompetes singlet exciton dissociation at the interface between donor and acceptor.