Alkynyl BODIPY-Core Bridged Perylene Diimide Star-Shaped Nonfullerene Acceptors for Efficient Polymer Solar Cells

Two new star-shaped perylene diimide (PDI)-based small-molecule acceptors denoted as BDP-3PDI and BDP-4PDI with BODIPY derivatives as the core and PDI units as peripheral groups were designed and successfully synthesized, and their photophysical and electrochemical properties were studied. When paired with a compatible D–A polymer donor P(BTT-DPP), the polymer solar cells based on the bulk heterojunction active layer attained power conversion efficiencies (PCEs) of about 10.97 and 13.94% for BDP-3PDI and BDP-4PDI, respectively. The higher value of PCE for BDP-4PDI is mainly owing to the enhanced values of the fill factor and short circuit current as compared to BDP-3PDI and related to the more balanced charge transport and blocked charge recombination owing to the appropriate phase separation in the P(BTT-DPP):BDP-4PDI active layer as compared to P(BTT-DPP):BDP-3PDI.