Si/CuIn_0.7Ga_0.3Se₂ Core–Shell Heterojunction for Sensitive and Self‐Driven UV–vis–NIR Broadband Photodetector

Abstract Designing Si nanowire‐based heterostructures provides a promising path to construct self‐driven and broadband photodetectors, which are the key components for optoelectronic systems. Herein, the first fabrication of a p‐CuIn_0.7Ga_0.3Se₂ nanoparticles/n‐Si nanowire array core–shell structure through a simple two‐stage process—spin coating and selenization treatment—and its integration into a self‐driven photodetector are reported. The heterojunction photodetector is sensitive to broad wavelength range from UV light to visible and near‐infrared light, with high detectivity of up to 1.6 × 10¹³ Jones, large responsivity of 0.33 A W⁻¹, and an ultrafast response speed of 823/356 µs at zero bias. Additionally, this core–shell nanostructure exhibits good air stability and strong ability to detect weak light sources such as fluorescent lamp and lighter. The superior performance can be attributed to the strong light absorption of both Si and CuIn_0.7Ga_0.3Se₂, the unique vertically standing core–shell structure, and effective photogenerated carriers' separation and transportation at the heterojunction interface.