Ultrathin TiO2 nanosheets synthesized using a high pressure solvothermal method and the enhanced photoresponse performance of CH3NH3PbI3-TiO2 composite films

In perovskite-TiO2 composite optoelectronic devices, a large grain size, a high percentage of {001} facets, TiO2 nanocrystals with high crystallinity, and good interconnectivity between both TiO2 and perovskite particles are crucial for the excellent performance of a hybrid photodetector. In this work, a high pressure hydrothermal method was developed to synthesize highly crystalline ultrathin (2-3 nm) TiO2 nanosheets bound with a high percentage of {001} facets. When these TiO2 nanosheets were utilized in the fabrication of perovskite-TiO2 composite photodetectors, a strikingly increased responsivity and detectivity were achieved. Furthermore, when the films were subjected to high pressure thermal treatment, both the particle size and the uniformity of the composite films greatly increased, resulting in a better performance of the hybrid photodetectors.