In situ grown Bi2S3 nanorods in Cs3Bi2I9 thin films as broadband self-driven photodetector with improved photostability

This study reports in-situ growth of bismuth sulfide (Bi2S3) nanorods incorporated cesium bismuth iodide (Cs3Bi2I9) thin films with improved photostability using a single-step ultrasonic spray deposition. The spray deposition was done using a non-aqueous solution containing CsI (0.0025 M), BiI3 (0.005 M), and thioacetamide in acetone, by varying concentrations of thioacetamide (0.005, 0.009, 0.01, 0.03 and 0.05 M) and the substrate temperature was 200 °C. The structure, morphology, and composition analysis of the films showed the formation of Cs3Bi2I9 thin films decorated with vertically aligned Bi2S3 nanorods in the intergranular region. The in situ-grown Cs3Bi2I9:Bi2S3 composite thin films were photosensitive and photostable. The photodiode of FTO/CdS/Cs3Bi2I9:Bi2S3/C–Ag demonstrated a stable spectral response for a wide wavelength range (405–1064 nm), with a detectivity of 8.18 × 109 Jones and responsivity of 0.59 mAW−1 under 532 nm illumination, operating in self-driven mode.