Significant enhancement of photovoltaic performance through introducing S•••N conformational locks

In this contribution, we developed a novel type of IDT-based small molecular acceptor, IDT-Tz, using thiazole as pi-bridges. Through employing thiazole units as the pi-bridges, nitrogen center dot center dot center dot sulfur noncovalent conformational locks were introduced to enhance the rigidity and planarity of the backbone, and thus reduce the reorganization energy, increase the charge transport mobility, and enhance the photovoltaic performance. The differences between the IDT-Tz and IDT-T based solar cells were fully investigated to understand the influences of the nitrogen center dot center dot center dot sulfur noncovalent conformational locks. The organic solar cells based on the IDT-Tz electron acceptor exhibit power conversion efficiencies (PCEs) as high as 8.4%, which is significantly higher than the PCE (4.1%) of the IDT-T based devices. This work demonstrated a novel strategy for enhancing the PCE of organic solar cells through introducing noncovalent conformational locks, which will be promising in designing novel high-performance non-fullerene materials.