Enhanced optical properties of lead-free double perovskite Cs2AgBiBr6 nanocrystals by doping of Na ions

Lead free double perovskite nanocrystals is an ideal alternate considering its nontoxic and stable property comparing with their counterpart lead halide perovskite NCs. A simple solution synthesis strategy was used to prepare lead-free double perovskite Cs2AgBiBr6 nanocrystals (NCs) doped with Na ions, resulting in NCs with a monodisperse state, homogeneous morphology, and good crystallinity. By adjusting the amount of Na+ doping, the band gap of the NCs was significantly increased from 2.57 eV to 3.00 eV. Furthermore, the relatively low value of photoluminescence quantum yield (PLQY) in the original Cs2AgBiBr6 NCs (-0.5%) was increased to about 8.5% when doped with 60% Na+. Additionally, the exciton lifetime of the NCs was extended to 16.15 ns compared to the original 2 ns. As a result, the doping of Na + significantly enhanced the PLQY of Cs2AgBiBr6 NCs, indicating their potential value for use in optoelectronic devices.