A Nonfullerene Acceptor with Alkylthio- and Dimethoxy-Thiophene-Groups Yielding High-Performance Ternary Organic Solar Cells

摘要

Herein, an A–D–A-type nonfullerene acceptor (named IDTS-4F) with an alkylthiophenyl side chain and dimethoxy thiophene bridging unit is reported. The useof an alkyl thiophenyl group is important, as the insertion of sulfur atoms canslightly downshift the highest occupied molecular orbital (HOMO) level of themolecule and allows IDTS-4F to match with state-of-the-art donor polymer PM6(or PM7). Compared with conventional nonfullerene acceptors, IT-4F, the IDTS-4F molecule, has a smaller optical bandgap and higher lowest unoccupiedmolecular orbital (LUMO) level, which are beneficial to increase the V_(oc) and J_(sc) ofthe devices. Nonfullerene organic solar cell devices are fabricated using IDTS-4F.Although the binary device based on IDTS-4F exhibits a lower fill factor (FF, 70%),the ternary device by incorporating 0.2 of IDTS-4F and 0.8 of IT-4F (with PM6 asthe donor polymer) can simultaneously achieve a higher Voc and Jsc, whilemaintaining the high FF (77%) of IT-4F based system. Morphology characterizationsindicate the formation of homogeneous film morphology, the largeincrease in phase purity and crystallinity, and the reduction in domain size uponaddition of crystalline IDTS-4F, while the electron/hole mobilities and recombinationlosses of the IT-4F system are both maintained.