CsSnBr3 and Cs3Bi2Br9: Structural, Optical Characteristics, and Application in a Schottky Barrier Diode

The search for alternatives to Pb-based perovskites, due to concerns about stability and toxicity, has led to the exploration of Pb-free options. Tin (Sn) and bismuth (Bi) are promising candidates, given their similar ionic radii to Pb and the isoelectronic nature of Pb²⁺ and Bi³⁺, which suggest comparable chemical properties. Among these, CsSnBr₃ and Cs₃Bi₂Br₉ are relatively underexplored but offer lower toxicity and enhanced stability while demonstrating optoelectronic properties suitable for various applications. In this study, CsSnBr₃ and Cs₃Bi₂Br₉ nanocrystals are synthesized using a colloidal method and integrated into Schottky diodes. X-ray photoelectron spectroscopy analysis of the surface chemistry confirms improved thermal and phase stability compared to Pb-based perovskites. Schottky diode parameters, including ideality factor, barrier height, and series resistance are assessed using conventional thermionic emission, modified Cheung's, and Norde's models. The Cs₃Bi₂Br₉-based Schottky diode exhibits superior electrical performance with the lowest series resistance and optimal barrier height. Electrical impedance spectroscopy results indicated that CsSnBr₃ has higher resistances and lower capacitances than Cs₃Bi₂Br₉, reflecting lower charge carrier mobility and more defects, although the R₁C₁ regions in both materials demonstrated faster charge dynamics, making them ideal for high-speed applications.