Non-fused ring electron acceptors with an ethynylene linker for non-halogenated solvent-processed organic solar cells

This study explores the design, synthesis and application of two non-fused ring electron acceptors (NFREAs), namely PAcT-Cl and CAcT-Cl, featuring an ethynylene linker, in non-halogenated solvent-processed organic solar cells (OSCs). The introduction of the ethynylene linker is found to effectively regulate the energy levels and molecular conformations of the acceptors. PAcT-Cl, with an alkoxy phenyl group core, exhibits downshifted highest occupied molecular orbital energy levels, higher electron mobility, and enhanced molecular packing order in neat thin films compared to CAcT-Cl, which incorporates a 4H-cyclopenta[1,2-b:5,4-b′]dithiophene core. As a result, the J52:PAcT-Cl device processed with o-xylene achieves a power conversion efficiency (PCE) of 10.22%, attributed to efficient charge transport and improved crystallinity, outperforming the OSC based on CAcT-Cl with inferior crystallinity (PCE = 7.32%). Furthermore, this study investigates the performance of PAcT-Cl-based devices processed with different solvents. Overall, this work demonstrates the application of an ethynylene linker in efficient NFREAs and discloses the potential of non-halogenated solvents for preparing NFREA-based devices.