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

In this study, die well-defined coil-rod-coil triblock copolymer poly(4-vinyltnphenylamme)-b-poly(3-hexylthiophene)-b-poly(4-vinyltriphenylamin) (PTPA-P3HT-PTPA) was used as a surfactant for P3HT/PCBM (I I) 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 I 5G (100 mW/cm(2)) 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 15% 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-VITA resulted in the balanced hole and electron mobility (mu(c)/mu(h) similar to 1 7 in comparison to the ratio of 3 6 without the surfactant) The incorporated PTPA-P3HT-PTPA surfactant not only extended the lifetime of solar cells but also reduced the PCBM aggregation upon annealing, resulting in better thermal stability The DSC result confirmed the selective miscibility of the VITA coil segment with PCBM These results demonstrated the superior compatibilizing effect of the rod coil triblock copolymers for solar cell applications