Fullerene bisadduct as an effective phase-separation inhibitor in preparing poly(3-hexylthiophene)-[6,6]-phenyl-C ₆₁-butyric acid methyl ester blends with highly stable morphology

This work demonstrates that the bis-adduct of [6,6]-phenyl-C ₆₁-butyric acid methyl ester (PCBM) is an effective inhibitor of the aggregation of PCBM inside the poly(3-hexylthiophene) (P3HT) matrix. Substituting some of the PCBM with bis-PCBM apparently reduces the size of PCBM-rich clusters, enhancing both the short-circuit current density (J _SC) and the fill factor (FF), leading to a ∼17% increment in power conversion efficiency (PCE) for a cell with 8.3 wt% bis-PCBM replacement. More importantly, a tiny amount of bis-PCBM significantly improves the morphological stability of P3HT-PCBM blend against high-temperature aging. All P3HT-PCBM:bis-PCBM devices exhibit extremely stable PCEs, which do not visibly change upon heating at 150 °C for 15 hours.