A Self-Powered Photodetector Based on MAPbI Single-Crystal Film/n-Si Heterojunction with Broadband Response Enhanced by Pyro-Phototronic and Piezo-Phototronic Effects.

Pyro-phototronic and piezo-phototronic effect have shown their important roles for high performance heterojunction-based photodetectors (PDs). Here, a coupling effect of pyro-phototronic and piezo-phototronic effect is utilized to fabricate a self-powered and broadband PD based on the MAPbI single-crystal film/n-Si heterojunction. First, by using the pyro-phototronic effect derived from MAPbI , the maximum photoresponsivity of the self-powered PD is 1.5 mA W for 780 nm illumination, which is enhanced by more than 20 times in consideration of the relative peak-to-peak output current. Light-induced temperature change in MAPbI film will create pyro-charges distributed at heterojunction interface, resulting in a downward bending of the energy band, facilitating the transport of photon-generated electrons and holes, and generating spike-like output currents. Second, piezo-phototronic effect is further introduced by applying vertical pressures onto the PD. With a vertical pressure of 155 kPa, the responsivity can be improved by more than 120% compared to the condition with no pressure. The overall enhancement is due to the piezo-phototronic and pyro-phototronic coupling effects which utilize the polarization charges to modulate the band structure of heterojunction. These results provide a promising approach to develop high-performance self-powered and broadband perovskite-based PDs by coupling pyro-phototronic and piezo-phototronic effect.