Design and synthesis of soluble dibenzosuberane-substituted fullerene derivatives for bulk-heterojunction polymer solar cells

Briefs: We have successful synthesized two fullerene derivatives, dibenzosuberane-C60 mono-adduct (DBSCMA) and bis-adduct (DBSCBA) with new spiral structure by cyclopropanation reaction for use as acceptor materials in polymer solar cells. The introduced dibenzosuberane groups improve the fullerene energy level alignment and the two new fullerene derivatives show slightly higher absorption in the visible region than conventional PCBM. After systematical optimization, a high power conversion efficiency of 3.70% was obtained for the devices using DBSCBA under an illumination of AM 1.5 G at 100 mW/cm2, which is 10% higher than that of P3HT:PCBM control device. The improved PCE is attributed to the optimal morphology and enhanced absorbance of DBSCBA in the visible region.