Synthesis of donor-acceptor rod-coil diblock copolymer compatibilizer and its effect on the morphology and performance of polythiophene:fullerene solar cells

Abstract

The synthesis of well-defined rod-coil block copolymers consisting of P3HT donor and C60 acceptor chromophores (P3HT-b-P(StyBAzx)-C60) in a molecular architecture is reported for use in bulk-heterojunction (BHJ) solar cells. In thin films of the resulting block copolymer, reproducible self-assembly into well-defined “nanofibrils” is observed. We find a substantial improvement in device performance when 10% of block copolymer is introduced to the P3HT:PCBM blend system, resulting in ca. 15% improved efficiency relative to the P3HT:PCBM solar cell fabricated without the “surfactant”. In addition, the diblock-copolymer additives employed stabilize device structure against destructive thermal phase segregation, which may also indicate a feasible strategy to improve device longevity.