Enhanced intramolecular charge transfer of unfused electron acceptors for efficient organic solar cells

Abstract

It is promising, yet challenging, to employ molecules of slight synthetic complexity to construct efficient and low-cost organic solar cells (OSCs). Herein, two unfused acceptors, DF-TCIC and HF-TCIC, were developed for OSC applications, in which the 3,4-difluorothiophene core connected through a cyclopentadithiophene (CPDT) bridge to 1,1-dicyanomethylene-3-indanone derivatives (IC for DF-TCIC and DFIC for HF-TCIC, respectively). As mediated by intramolecular non-covalent interactions, these unfused acceptors exhibited a nearly planar structure, and a strong charge transfer effect. HF-TCIC-based OSCs showed a high short-circuit current density (J_sc) of 20.04 mA cm⁻² and a power conversion efficiency (PCE) of 9.86%, thereby outperforming DF-TCIC-based devices (J_sc of 16.39 mA cm⁻² and PCE of 8.23%). This work suggests that unfused acceptors of slight synthetic complexity are promising for OSC applications.