Enhancement of P3HT/PCBM Photovoltaic Efficiency Using the Surfactant of Triblock Copolymer Containing Poly(3-hexylthiophene) and Poly(4-vinyltriphenylamine) Segments

In this study, the well-defined coil−rod−coil triblock copolymer poly(4-vinyltriphenylamine)-b-poly(3-hexylthiophene)-b-poly(4-vinyltriphenylamin) (PTPA-P3HT-PTPA) was used as a surfactant for P3HT/PCBM (1:1) based solar cells. The power conversion efficiency of the device was enhanced from 3.9 to 4.4% in the presence of the 0−5% PTPA-P3HT-PTPA under illumination of AM 1.5G (100 mW/cm2). The morphology variation and the balance of the hole/electron mobility accounted for such enhancement. In the P3HT/PCBM/PTPA-P3HT-PTPA ternary blends, the fiber-like structure was observed for surfactant ratios of 0−5%, while a sphere-like nanostructure was observed for the surfactant ratio of 1.5%. The sphere-like nanostructure led to a smaller domain size and enhanced interfacial area for charge separation as compared to the fiber-like structure. On the other hand, the increased hole mobility in the blend with the addition of PTPA-P3HT-PTPA resulted in the balanced hole and electron mobility (μe/μh ∼1.7 in comparison to...