Enhancing the performance of non-fullerene organic solar cells through side-chain engineering of asymmetrical non-fused-ring electron acceptors

In organic solar cells (OSCs), the intricate synthesis and lower yield of ladder-type fused ring small molecule receptors (FR-SMAs) have prompted the quest for simpler, higher yielding non-fused ring (NFR)-SMAs. In this paper, a type of NFR asymmetrical SMA with an A-D-pi-A structure, namely DPCT8-4F and DPCT10-4F, was primarily designed and synthesized, in which an alkyl chain dipyran (DP) ring, cycllopentadithiophene (CT) and fluorinated 1,1-dicyanomethylene-3-indanone (4F) are employed as the donor (D) unit, pi-bridge and acceptor (A) terminals, respectively. The influence of the alkyl chain originating from the DP unit on their optical, electrochemical and photovoltaic properties was systematically investigated. The DPCT8-4F with n-octane chains exhibited enhanced crystallinity and molecular packing compared to the DPCT10-4F with n-decane chains. After being blended with the polymer donor PBDB-T, the OSCs based on PBDB-T:DPCT8-4F demonstrate an impressive power conversion efficiency (PCE) of 12.52%, surpassing that of 11.68% for the DPCT10-4F-based ones. This work demonstrates that these asymmetric NFR-SMAs can improve the efficiency of OSCs by pairing alkyl chains on the dipyran ring. In organic solar cells (OSCs), the intricate synthesis and lower yield of ladder-type fused ring small molecule receptors (FR-SMAs) have prompted the quest for simpler, higher yielding non-fused ring (NFR)-SMAs.