Enhanced Photoresponse in Few-Layer SnS₂ Field-Effect Transistors Modified with Methylammonium Lead Iodide Perovskite

We demonstrate that decoration with methylammonium lead iodide perovskite (MAPbI3) nanoparticles is an efficient approach to engineer strong visible light photoresponse in electronic devices based on two-dimensional (2D) materials with limited optical absorptivity. This approach was demonstrated using 2D SnS2, a promising electronic material with a band gap of about 2.3 eV and poor absorption in the visible range of spectrum. Field-effect transistors based on pristine 2D SnS2 show an n-type transport with high on–off ratios. Decoration with isolated MAPbI3 nanoparticles qualitatively retains the transfer characteristics of the devices but dramatically increases their photoresponse in the entire visible range of the spectrum. In particular, the photoresponse of the MAPbI3-decorated devices to the red light is entirely engineered by the perovskite modification of SnS2, which by itself does not absorb in the red region of the spectrum. The MAPbI3-decorated SnS2 devices exhibit stable, reproducible photoswitching over numerous cycles with response times of no longer than 12 ms. An analysis of a MAPbI3–SnS2 heterostructure by Kelvin probe force microscopy resulted in an energy level diagram suggesting a transfer of the photoexcited electrons in MAPbI3 to the conduction band of the n-type SnS2 channel. The photoresponse characteristics of the perovskite-modified SnS2 devices were shown to be consistent with the intrinsic optical properties of MAPbI3. The described perovskite decoration approach should be applicable to engineering photoresponse in a variety of other devices based on 2D electronic materials with low optical absorptivity.