High Performance Lead‐Free Perovskite‐Based Photodetector for Low‐Light Intensity Detection in Biomedical Applications

This work presents a comprehensive numerical study on a lead-free, tin-based perovskite photodetector (PPD) designed for low-light biomedical sensing applications. Using CH₃NH₃SnBr₃ as the active absorber layer, we model a device architecture comprising FTO/CdZnS/CH₃NH₃SnBr₃/Spiro-OMeTAD/Au, optimizing key parameters through combined SCAPS-1D and COMSOL Multiphysics simulations. We systematically investigate the influence of absorber thickness, defect density, donor doping, electric field distribution, series and shunt resistance, and interface properties to maximize optoelectronic performance. The optimized PPD achieves a peak responsivity of 0.55 A/W and a detectivity of 9.7 × 10¹⁴ Jones within the red-light spectral window (680-790 nm), demonstrating enhanced charge carrier lifetimes and effective interfacial charge extraction. These results highlight the potential of CH₃NH₃SnBr₃ as an eco-friendly alternative to lead-based perovskites, advancing the development of high-sensitivity, low-illumination photodetectors for biomedical imaging and diagnostics.