  Heterovalent substitution of toxic lead is an increasingly popular design
strategy to obtain environmentally sustainable variants of the exciting
material class of halide perovskites. Perovskite nanocrystals (NCs) obtained
through solution-based methods exhibit exceedingly high optical quality.
Unfortunately, most of these synthesis routes still require reaction under
inert gas and at very high temperatures. Herein we present a novel synthesis
routine for lead-free double perovskite NCs. We combine hot injection and
ligand-assisted reprecipitation (LARP) methods to achieve a low-temperature and
ambient atmosphere-based synthesis for manganese-doped Cs_{2}NaBiCl_{6} NCs. Mn
incorporation is critical for the otherwise non-emissive material, with a 9:1
Bi:Mn precursor ratio maximizing the bright orange photoluminescence (PL) and
quantum yield (QY). Higher temperatures slightly increased the material's
performance, yet NCs synthesized at room temperature were still emissive,
highlighting the versatility of the synthetic approach. Furthermore, the NCs
show excellent long-term stability in ambient conditions, facilitating
additional investigations and energy-related applications.
