Lead-free double perovskites (DPs) with excellent moisture, light, and heat stability have been explored as alternatives to toxic lead halide perovskite (APbX 3 ) (A for monovalent cation and X for Cl, Br, or I). However, the bandgaps of the current DPs are generally larger and either indirect or direct forbidden, which leads to weak visible light absorption and limitation for photovoltaic and other optoelectronic applications. Herein, we demonstrate the first synthesis of Cu 2+ -doped Cs 2 AgInCl 6 double perovskite nanocrystals via a facile hot-injection solution approach. The electronic bandgap can be dramatically tuned from ∼3.60 eV (Cs 2 AgInCl 6 , parent) to ∼2.19 eV (Cu 2+ -doped Cs 2 AgInCl 6 ) by varying the Cu 2+ doping amount. We conclude that the decrease of bandgap is attributed to the overlap of the Agd/In-p/Cl-p orbitals and the Cu-3d orbitals in the valence band. The wide tunability of the optical and electronic properties makes Cu 2+ -Doped Cs 2 AgInCl 6 DP NCs promising candidates for future optoelectronic device applications.

In this study, a facile approach is used to enhance the broad orange emission efficiency and stability as well as monodispersity of Cs 2 AgInCl 6 nanocrystals (NCs) via doping Bi 3+ and surface passivation with potassium bromide. While the pristine Cs 2 AgInCl 6 NCs show an excitonic absorption peak at 280 nm, the doped NCs have an additional absorption peak at 365 nm, which is attributed to direct bismuth s−p transition. Compared to the low photoluminescence (PL) quantum yield (QY) of 0.04% for the pristine Cs 2 AgInCl 6 NCs due to parity forbidden transition, the doped NCs show a PLQY of 5.82%, a significant improvement due to breaking of the parity forbidden transition. The PLQY can be further increased to 8.59% for Cs 2 AgIn 0.9 Bi 0.1 Cl 6 when passivated with KBr. This work demonstrates that the combination of doping and surface passivation can substantially improve the PL of the Cs 2 AgInCl 6 double perovskite. A model is proposed to explain the observed enhancement in PL and stability.