A high-performance non-fullerene electron acceptor with bisalkylthiothiophene pi-bridges for organic photovoltaics

A new non-fullerene small molecule acceptor IDT2ST-4F bearing a bisalkylthiothiophene unit as the pi-bridge was designed and synthesized, which exhibited a low optical bandgap of 1.43 eV. The optimized organic solar cells based on PBDB-T:IDT2ST-4F gave a high power conversion efficiency (PCE) of 11.43% with a relatively low energy loss of 0.58 eV.