Tunable Optoelectronic Properties of CsPbBr3 Perovskite Nanocrystals for Photodetectors Applications

Inorganic halide perovskite nanocrystals (NCs) have drawn considerable attention in recent years due to their improved stability, superior photophysical properties, and defect-tolerant nature, which allows for high carrier mobility and efficient charge transport in various optoelectronic devices. The bandgap and size of halide perovskite nanocrystals can be tuned through a variety of approaches, including cation/anion exchange, ligand modification, and precursor concentration adjustment. In this article, we investigate the effects of precursor concentration on the structural, optical, and electronic properties of cesium lead bromide (CsPbBr₃) nanocrystals. We have synthesized ∼13-50 nm nanocrystals from four different concentrations of precursor solutions. It has been observed that the excitonic absorption band increases with particle size as the precursor concentration decreases. The steady state photoluminescence intensity decreases due to a shorter carrier lifetime (in solution). We have fabricated photodetectors using four different-size samples and show that the photoresponsivity increases with increasing particle size. The nanocrystals synthesized from the diluted precursor solution (0.005 M) exhibits the highest detectivity of 2.84 × 10⁹ jones due to their larger crystal size and fewer defect states, which results in a higher carrier diffusion length with reduced free carrier recombination.