Room temperature synthesis and characterization of novel lead-free double perovskite nanocrystals with a stable and broadband emission

Low-dimensional and lead-free halide perovskites are of great interest for their wide application potential for optoelectronic applications. We report on the successful synthesis of novel lead-free colloidal Cs₃BiBr₆ nanocrystals (NCs) with an ultra-small size of ∼1.5-3 nm by a room temperature antisolvent process. From crystallographic characterization we show that it is critical to precisely control the ratio of precursors to obtain the pure 3-1-6 phase. The synthesis process is facile and repeatable and results in Cs₃BiBr₆ NCs that display stable blue emission around 438 nm with a relatively broad linewidth of 92.1 nm. Low-temperature photoluminescence (PL) measurements displayed a red-shift of bandgap with decreasing temperature, which might be attributed to the thermal expansion of the lattice. In addition, the NCs demonstrate high stability at ambient conditions.