Design of CsSnBr3/Ga2O3 Hybrid Photodetectors for High UV Selectivity and Bifacial Usage

The operation and characteristics of a novel all-inorganic hybrid p–n heterojunction, formed by lead-free perovskite CsSnBr3 deposited on Ga2 O3 , are numerically investigated. Key performance parameters such as current–voltage behavior, quantum efficiency (QE), spectral responsivity (R), detectivity (D * ), noise-equivalent power (NEP), and band alignment are analyzed. Results show a high illumination-to-dark current ratio of 107 and a rectification ratio of ≈7.6 × 10 6 (in dark) and 1.33 × 10 4 (under illumination) at ±3 V. The CsSnBr 3 /Ga 2 O3 photodetector supports bifacial, self-powered, solar-blind, and ultraviolet-visible (UV–Vis) detection modes by adjusting layer thickness and doping concentration. In selective UV mode, it achieves a responsivity of 57.5 mA/W, detectivity of 3.6 × 10 10 Jones, and noise-equivalent power of 9.84 × 10−12 W∕√Hz. In the UV–Vis mode, these improve to 161 mA/W, 1 × 10 11 Jones, and 3.51 × 10−13 W∕√Hz, respectively. The device also shows an effective visible-light detection upon reversing the illumination direction, indicating potential use in stacked solar cells. This study outlines critical design parameters and optimization strategies, paving the way for future research on stable, lead-free, all-inorganic hybrid devices combining perovskites with wide-bandgap semiconductors.