Highly efficient bulk heterojunction photovoltaic cells based on C70 and tetraphenyldibenzoperiflanthene

Abstract

Highly efficient photovoltaic cells based on a bulk heterojunction configuration composed of C₇₀ with various donor materials at 5 wt. % donor concentration were fabricated. The tetraphenyldibenzoperiflanthene (DBP) donor achieved the highest power conversion efficiency (η_PCE) of 6.4% for the optimized cell. The improved performance with DBP arises from a combination of a higher absorption coefficient than 1,1-bis-(4-bis(4-methyl-phenyl)-amino-phenyl)-cyclohexane and a symmetrical molecular structure. The high η_PCE with only 5 wt. % donor is attributed to a sufficient donor concentration for enhanced Frenkel exciton dissociation in C₇₀, while efficiency and electron mobility decrease at higher donor concentrations.