Rational design of truxene-bridged PDI trimers as acceptors for efficient organic solar cells

Three different truxene-bridged perylenediimide (PDI) trimers are designed and synthesized. The truxene core and the PDI unit are linked by a triple bond (T-PDI), carbon-carbon single bond (S-PDI) and ring-fused linker (R-PDI). The effects of three linkage modes on the photophysical, electrochemical and photovoltaic properties of the acceptors are systematically investigated. Bulk heterojunction solar cells by using the truxene-bridged PDI trimers as electron acceptor and a commercial material (PTB7-Th) as electron donor were fabricated. The results demonstrate that the linkage mode between truxene and PDI units plays an important role in determining photovoltaic performances of non-fullerene electron acceptors. The R-PDI acceptor with ring-fused linker shows the highest power conversion efficiency (PCE) of 4.19% owning to its appropriate morphology, high charge mobility, and high open-circuit voltage (Voc) of 1.0 V.