Tuning morphology, stability and optical properties of CsSnBr₃ nanocrystals through bismuth doping for visible-light-driven applications

In this investigation, we have demonstrated the synthesis of lead-free, CsSnBr₃ (CSB) and 5 mol% bismuth (Bi) doped CSB (CSB′B) nanocrystals, with a stable cubic perovskite structure following a facile hot injection technique. The Bi substitution in CSB was found to play a vital role in reducing the size of the nanocrystals significantly, from 316±93 to 87±22 nm. Additionally, Bi doping has inhibited the oxidation of Sn²⁺ of CSB perovskite. A reduction in the optical band gap from 1.89 to 1.73 eV was observed for CSB′B and the PL intensity was quenched due to the introduction of Bi³⁺ dopant. To demonstrate one of the visible-light-driven applications of the nanocrystals, photodegradation experiments were carried out as a test case. Interestingly, under UV-vis irradiation, the degradation efficiency of CSB′B is roughly one order lower than that of P25 titania nanoparticles, however, it is almost five times higher when driven by visible light under identical conditions. Moreover, by employing experimental parameters, DFT-based first-principles calculations were performed, which demonstrated an excellent qualitative agreement between experimental and theoretical outcomes. The as-synthesized Bi-doped CSB might be a stable halide perovskite with potential in visible-light-driven applications.