Halide-Triggered Oxidative Etching as a Key Step in the Formation of Lead-Free Double Perovskite Nanocrystals

The colloidal synthesis of Ag-based lead-free double perovskite nanocrystals (NCs) involves Ag⁺-reduction mediated pathways, however, the role of Ag redox chemistry in lattice formation remains poorly understood. Here, we elucidate the crystallization-driven redox processes that govern the formation of Cs₂AgBiBr₆ NCs. An alternative synthesis has been proposed by carefully studying the effect of reaction temperature behind the in-situ Ag-reduction aided from Ag-oleate complex decomposition at >175 °C, followed by its oxidation mediated by the addition of exclusively used halide precursor, oleylammonium bromide (OLAmBr). The halide precursor participates in the oxidation of in-situ formed Ag⁰ followed by the crystallization of Cs₂AgBiBr₆ NCs. This work establishes halide-mediated oxidative etching as a key step in the crystallization of lead-free double perovskite NCs.