Liquid Crystal Helps ZnO Nanoparticles Self-Assemble for Performance Improvement of Hybrid Solar Cells

We offer a novel approach to improve the performance of poly 3-hexylthiophene (P3HT)/ZnO hybrid photovoltaic devices by binding the 4,7-diphenyl-2,1,3-benzothiadiazole-based liquid crystal (LC) with a monothiol end group onto the surface of ZnO nanoparticles (LC-ZnO). The attachment of LC onto ZnO nanoparticles’ surfaces can improve the dispersion of ZnO nanoparticles and can endow the ZnO nanoparticles self-assembled behavior upon annealing at LC state temperature (160 °C). By use of the LC-ZnO as electron acceptors in hybrid solar cells enhances the order and crystallinity of P3HT chains and evolves the microstructure of P3HT/LC-ZnO blend, enabling short-circuit current density ( J sc ) to be increased. More interestingly, the order of the P3HT/LC-ZnO blend morphology is significantly enhanced after thermal treatment at 160 °C, indicating that the spontaneous assembly of the LC-ZnO pushes P3HT chains to form oriented nanodispersing structure with highly oriented channel layers upon only heating at LC states, leading to the improved power conversion efficiency by 1.8 fold compared with the device based on P3HT/ZnO, demonstrating that the described self-assembled LC-ZnO hybrids represent a promising strategy toward nanoscale controlled bulk heterojunction solar cells.