Ring Fusion of Thiophene–Vinylene–Thiophene (TVT) Benefits Both Fullerene and Non-Fullerene Polymer Solar Cells

Abstract

Conjugated polymers based on thiophene–vinylene–thiophene (TVT) and ethenylene fused TVT (ETVT) combined with alkylated dithienylbenzothiadiazole (DTBT) were designed and synthesized to investigate the effect of ring fusion on the properties of TVT based photovoltaic polymers. It is found that ring fusion of the TVT segment significantly affects molecular architecture and optoelectronic properties of the polymer. Ring fusion can downshift the HOMO energy level and increase the absorption coefficient of the corresponding polymer. Combining with reduced energy loss, PETVTTBT shows superior photovoltaic performance to PTVTTBT, in both fullerene and non-fullerene polymer solar cells. Particularly, in ITIC based polymer solar cells, simultaneous enhancement in the JSC, VOC, and FF is demonstrated after ring fusion. As a result, PCE of PETVTTBT based solar cells increases drastically by 120% over that of PTVTTBT (3.69%), reaching 8.18%.