Novel perovskite/TiO2/Si trilayer heterojunctions for high-performance self-powered ultraviolet-visible-near infrared (UV-Vis-NIR) photodetectors

Methylammonium lead halide perovskites have been reported to be promising candidates for high-performance photodetectors. However, self-powered broadband ultraviolet-visible-near infrared (UV-Vis-NIR) photodetection with high responsivity is difficult to achieve in these materials. Here, we demonstrate, for the first time, a novel trilayer hybrid photodetector made by combining an n-type Si wafer, TiO2 interlayer and perovskite film. By precisely controlling the thickness of the TiO2 layer, enhanced separation and reduced recombination of carriers at the Si-perovskite interface are obtained. As a result, perovskite film, when combined with a low-bandgap Si, extends the wavelength range of photo response to 1,150 nm, along with improved on/off ratio, responsivity, and specific detectivity, when compared to pristine perovskite. Results obtained in this work are comparable or even better than those reported for perovskite-based UV-Vis-NIR photodetectors. In particular, the hybrid photodetectors can operate in a self-powered mode. The mechanism of enhancement has been explored and it is found that the increased separation and reduced recombination of photogenerated carriers at the junction interface leads to the improved performance.