Morphological Stabilization by Supramolecular Perfluorophenyl-C_(60) Interactions Leading to Efficient and Thermally Stable Organic Photovoltaics

摘要

A new PC_(61)BM-based fullerene, [6,6]-phenyl-C_(61) butyric acid pentafluoro-phenyl ester (PC_(61)BP~F) is designed and synthesized. This new n-type material can replace PC_(61)BM to form a P3HT:PC_(61)BP~F binary blend or serve as an additive to form a P3HT:PC_(61) BM:PC_(61)BP~F ternary blend. Supramolecular attraction between the pentafluorophenyl group of PC_(61)BP~F and the C_(60) cores of PC_(61)BP~F/PC_(61)BM can effectively suppress the PC_(61)BP~F/PC_(61)BM materials from severe aggregation. By doping only 8.3 wt% PC_(61)BP~F, device PC_(61)BP~F651 exhibits a PCE of 3.88% and decreases slightly to 3.68% after heating for 25 h, preserving 95% of its original value. When PC_(61)BP with non-fluorinated phenyl group is used to substitute PC_(61)BP~F, the stabilizing ability disappears completely. The efficiencies of PC_(61)BP651 and PC_(61)BP321 devices significantly decay to 0.44% and 0.11%, respectively, after 25 h isothermal heating. Most significantly, this strategy is demonstrated to be effective for a blend system incorporating a low band-gap polymer. By adding only 10 wt% PC_(61)BP~F, the PDTBCDTB:PC_(71)BM-based device exhibits thermally stable morphology and device characteristics. These findings demonstrate that smart utilization of supramolecular interactions is an effective and practical strategy to control morphological evolution.