Investigation of Quinquethiophene Derivatives with Different End Groups for High Open Circuit Voltage Solar Cells

Abstract Three quinquethiophene derivatives with different end groups of octyl 2‐cyanoacetate (DCAO5T), 3‐ethylrhodanine (DERHD5T) and 2H‐indene‐1,3‐dione (DIN5T) are synthesized in order to obtain higher open circuit voltage (V_oc) than their septithiophene analogs. The photovoltaic performance of these three molecules as donors and fullerene derivatives as the acceptors in bulk heterojunction solar cells are studied by using the simple solution spin‐coating fabrication process. Among them, DERHD5T shows V_oc as high as 1.08 volt and power conversion efficiency of 4.63% under AM 1.5G irradiation (100 mW cm⁻²). The reasons for the high V_oc were investigated by the theoretical simulations and consistent results have been obtained in comparison with experimental measurements.