Highly efficient, self-powered UV photodiodes based on leadfree perovskite nanocrystals through interfacial engineering

Double perovskite crystals are promising alternatives for lead-based perovskites that has potential to address toxicity and instability issues. In this study, Cs₂AgBiCl₆nanocrystals (NCs) with high absorption coefficients were synthesized by hot-injection method. The bandgap engineering was realized by tuning the halide composition in Cs₂AgBiCl₆to Cs₂AgBiBr₆. Both NCs were used as light-absorbing layers in lead-free perovskite photodiodes that exhibit wavelength-selectivity for UV-visible light operatable even at a bias voltage of 0 V. Cs₂AgBiBr₆-based photodiode exhibits a characteristic detection peak at 340 nm with a responsivity of 3.21 mA W^-1, a specific detectivity up to 8.91 × 10¹⁰Jones and a fast response speed with a rise/fall time of 30/35 ms. The excellent performance of self-driven photodiodes lights up the prospect of lead-free perovskite NCs in highly efficient optoelectronic devices.