Effect of TiO2 Nanoparticles on Self-Assembly Behaviors and Optical and Photovoltaic Properties of the P3HT-b-P2VP Block Copolymer

An ordered nanostructure can be created from the hybrid materials of self-assembly poly(3-hexyl thiophene-b-2-vinyl pyridine) and nicotinic acid-modified titanium dioxide nanoparticles (P3HT-b-P2VP/TiO2). TEM and XRD analyses reveal that the TiO2 nanoparticles (NPs) are preferentially confined in the P2VP domain of P3HT-h-P2VP whereas TiO2 NPs interact with either pure P3HT or a blend of P3HT and P2VP to produce microsizcd phase segregation. The morphologies of lamellar and cylindrical structures are disturbed when the loading of TiO2 NPs is 40 wt % or higher. Cylindrical P3HT-b-P2VP/TiO2 exhibits a small blue shift in absorption and photoluminescence spectra with increasing TiO2 loading as compared to P3HT/TiO2. The NPs cause a slightly misaligned P3HT domain in the copolymer. Furthermore, the PL quenching of P3HT-b-P2VP/TiO2 becomes very large as a result of efficient charge separation in the ordered nanodomain at 16 nm. Solar cells fabricated from self-assembly P3HT-b-P2VP/TiO2 hybrid materials exhibit a > 30 fold improvement in power conversion efficiency as compared to the corresponding 0.3P3HT-0.7P2VP/TiO2 polymer blend hybrid. This study paves the way for the further development of high-efficiency polymer inorganic nanoparticle hybrid solar cells using a self-assembled block copolymer.