Three dimensional multi-arm acceptors based on diketopyrrolopyrrole with (hetero)aromatic cores for non-fullerene organic solar cells without additional treatment

Two multi-arm acceptors based on diketopyrrolopyrrole (DPP) segments and either a tetraphenylethylene (TPE) or spirobicyclopentadithiophene (SCPDT) core, named TPE-4DPPDCV and SCPDT-4DPPDCV, were designed and synthesized as fullerene replacements for organic solar cells (OSCs). The acceptors with three dimensional structures showed uniform film morphologies of appropriate nano-phase separation when blended with a donor polymer. SCPDT-4DPPDCV exhibited broader UV–vis absorption profiles and improved charge transporting ability compared to TPE-4DPPDCV due to a better conjugation along the arms in SCPDT-4DPPDCV, which resulted in a higher power conversion efficiency (4.20%) in PTB7-TH:SCPDT-4DPPDCV solar cells than that of PTB7-TH:TPE-4DPPDCV (4.01%). This work implied three dimensional multi-arm acceptor is a promising approach for high performance non-fullerene based OSCs.