Effective control of solution self-assembly of P3HT/zinc salt complex for in situ template synthesis of P3HT/ZnO nanohybrids

This study explored the detailed solution self-assembly of a P3HT/zinc salt complex system as well as the following in situ growth mechanism of ZnO nanocrystals within self-assembled nanotemplates. Through controlling the solvent selectivity and aging conditions, the geometric shape of the complex system could be directly tailored in solution, forming nanoscopic spheres or highly elongated nanofibrils. These solution self-assembled nanostructures could be efficaciously transferred onto substrates to fabricate nanostructured hybrid films through drop casting. In contrast to traditional P3HT systems with only form I crystalline structure, nanostructured P3HT complex thin films revealed a metastable crystalline phase with overlapping alkyl side chains. The formation of this interdigitated crystalline feature could be attributed to the solvent evaporation-induced crystallization of tightly assembled complex chains existing in solution self-assembled nanostructured domains. The nanostructured P3HT/zinc salt complex assemblies were further used as nanoreactors for the in situ growth of ZnO. As complex samples were thermally treated, a phase transformation of P3HT from the metastable crystalline phase to form I structure as well as the formation of ZnO nanocrystals were clearly observed. Both nanospherical and nanofibrillar structured P3HT/ZnO hybrids exhibited lower photoluminescence intensity than did a P3HT/ZnO blend sample. In particular, the nanofibrillar structured hybrid provided an optimized donor/ acceptor structure for exciton dissociation as well as interpenetrating nanochannels for charge transport, resulting in the most effective photoluminescence quenching effect among measured samples. We believe that our study can serve as a model system and provide guidelines for efficiently controlling the hierarchical structures of pi-conjugated polymer/inorganic nanocrystal hybrids through the in situ synthesis, offering benefits for advanced photoelectronic applications.