Side-chain engineering of A-D-D-A-type small-molecule electron acceptors for high-performance polymer solar cells with Jsc exceeding 22 mA cm−2

Abstract One of the effective ways to improve the short-circuit current density (Jsc) of polymer solar cells (PSCs) is to develop near-infrared (NIR) nonfullerene small molecule acceptors (SMAs). Herein, a novel NIR acceptor-donor-donor-acceptor (A-D-D-A)-type SMAs, C6-IDT2-DFIC which is derived from previously reported IDT2-DFIC, was designed and synthesized. By replacing the phenylhexyl group with the hexyl side-chain, the C6-IDT2-DFIC exhibits a wide absorption range in the 550–900 nm, strong intermolecular interactions, higher and more balanced charge mobilities. The device with the PBDB-T:C6-IDT2-DFIC blend film showed a power conversion efficiency (PCE) of 12.33% with a Jsc of 22.57 mA cm−2, which is higher than that of the PBDB-T:IDT2-DFIC device (10.06% with a Jsc of 16.06 mA cm−2). More interestingly, the Jsc of the PBDB-T:C6-IDT2-DFIC device is one of the highest current densities from PBDB-T-based PSCs with optoelectronic response below 900 nm. Our work clearly indicate that side chain engineering is useful to achieve high Jsc of PSCs.