Synthesis, characterization, and optical studies of lead-free perovskite, Cs₃M₂Br₉ (M = Bi, Sb) nanocrystals

In recent years, there has been a surge in research interest surrounding all inorganic lead perovskite nanocrystals (NCs) owing to their exceptional performance in various optoelectronic devices. Nevertheless, the presence of lead and concerns regarding its toxicity and stability have cast a shadow over their potential wide-ranging applications. In this study, we present the synthesis of two lead-free all-inorganic perovskite materials, Cs₃M₂Br₉ (where M = Bi or Sb), in bulk form, using an aqueous halide acid medium. Additionally, we describe a top-down approach for the fabrication of two lead-free all-inorganic perovskite, Cs₃M₂Br₉ (M = Bi or Sb) NCs. The Cs₃Sb₂Br₉ NCs display a sheet-like morphology, while Cs₃Bi₂Br₉ NCs exhibit a cubic structure. The PL spectra of Cs₃Sb₂Br₉ and Cs₃Bi₂Br₉ NCs exhibit distinct emission peaks at 476 nm and 472 nm, respectively, with relatively narrow full width at half maximum (FWHM) of 44 nm and 38 nm, respectively. Cs₃Sb₂Br₉ and Cs₃Bi₂Br₉ NCs demonstrate excellent thermal stability up to 320 °C and 470 °C, respectively. Notably, the high photoluminescence quantum yield (PLQY) of these NCs, Cs₃Sb₂Br₉ NCs (31 %) and Cs₃Bi₂Br₉ NCs (36 %) are highly beneficial for optoelectronic applications is observed.