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

A new PC sub(61)BM-based fullerene, [6,6]-phenyl-C sub(61) butyric acid pentafluorophenyl ester (PC sub(61)BP super(F)) is designed and synthesized. This new n-type material can replace PC sub(61)BM to form a P3HT:PC sub(61)BP super(F) binary blend or serve as an additive to form a P3HT:PC sub(61)BM:PC sub(61)BP super(F) ternary blend. Supramolecular attraction between the pentafluorophenyl group of PC sub(61)BP super(F) and the C sub(60) cores of PC sub(61)BP super(F)/PC sub(61)BM can effectively suppress the PC sub(61)BP super(F)/PC sub(61)BM materials from severe aggregation. By doping only 8.3 wt% PC sub(61)BP super(F), device PC sub(61)BP super(F)651 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 sub(61)BP with non-fluorinated phenyl group is used to substitute PC sub(61)BP super(F), the stabilizing ability disappears completely. The efficiencies of PC sub(61)BP651 and PC sub(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 sub(61)BP super(F), the PDTBCDTB:PC sub(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. A new PC sub(61)BM-based fullerene, [6,6]-phenyl-C sub(61) butyric acid pentafluorophenyl ester (PC sub(61)BP super(F)) is presented. Supramolecular attraction between the pentafluorophenyl group of PC sub(61)BP super(F) and the C sub(60) cores of PC sub(61)BP super(F)/PC sub(61)BM can effectively suppress the n-type PC sub(61)BP super(F)/PC sub(61)BM materials from severe aggregation to mitigate the morphological evolution and preserve the device performance.