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 (ηPCE) 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 ηPCE 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.