Flexible, stable, and self-powered photodetectors embedded with chemical vapor deposited lead-free bismuth mixed halide perovskite films

The emerging revolution in the field of Internet of Things (IoT) necessitates the development of flexible, self -powered, and cost-effective photodetectors such as metal halide-based perovskite photodetectors. Lead-free ternary metal halides have emerged as a promising option having no technical barrier with regard to toxicity. However, the performance metrics of lead-free ternary metal-halide-based optoelectronic devices lags behind those of conventional lead-halide-based devices. In this study, we demonstrate that chemical-vapor-deposited methylammonium bismuth iodide (MA3Bi2I9 (MBI)) films and their mixed halide analogues (MA3Bi2I6Br3 (MBIB)) and MA3Bi2I6Cl3 (MBIC)) enhance the performance metrics and stability of photodetectors by enabling the growth of films with smooth and compact morphology. MBIC-integrated devices achieved a responsivity of -0.92 A/W and specific detectivity of -2.9 x 1013 Jones under no bias and UV (382 nm) illumination, which is approximately-three times higher than MBI counterparts. They also exhibit outstanding operational stability by maintaining 94 % of the photoresponse after illumination for 500 h (382 nm wavelength at light intensity of 1.0 mW/cm2) in ambient air. Furthermore, these devices show satisfactory mechanical stability, with the attenuation being as low as 15 % of initial photoresponse after bending for 5,000 cycles at 5 % tensile strain. Our findings indicate that MBIC film-integrated devices have immense potential in optoelectronics.