The influence of polymer purification on the efficiency of poly(3-hexylthiophene):fullerene organic solar cells

Abstract

We report the influence of different polymer purification procedures on the photovoltaic performance of bulk heterojunction solar cells formed from binary blends of poly(3-hexylthiophene) (P3HT) and fullerenes. Selective Soxhlet extractions and metal scavenging agents were used to remove residual monomer, magnesium salt by-products and catalyst from high-weight P3HT (Mw 121 kg/mol, PDI 1.8, RR 99%) synthesised by the Grignard metathesis (GRIM) polymerization route. Using phenyl-C61-butyric acid methyl ester (PC 60 BM) as an electron acceptor, we observed an increase in average power conversion efficiency from 2.3 to 4.8% in going from crude to fully purified material. Using indene-C 60 bisadduct (IC 60 BA) in place of PC 60 BM, we observed a further increase to an average value of 6.6%-high for a bulk heterojunction formed from a binary blend of P3HT and C 60 fullerene derivatives.