Highly Efficient White‐Light Emission Triggered by Sb3+ Dopant in Indium‐Based Double Perovskites

Inorganic indium‐based halide double perovskites (DPs) are environmentally friendly alternatives to lead‐based halide perovskites in light‐emitting diodes, but commonly suffer from low quantum efficiency and harsh synthesis conditions. Herein, a large‐scale green method using water as solvent is developed for the synthesis of 3D Cs 2 NaInCl 6 and 0D Cs 2 InCl 5 ·H 2 O with/without Sb 3+ dopant at room temperature. The transformation between Cs 2 InCl 5 ·H 2 O and Cs 2 NaInCl 6 products is controlled by the concentration of eco‐friendly NaCl, where excess Cl − and Na + ions play important roles in inhibiting In 3+ hydrolysis and promoting Cs 2 NaInCl 6 crystallization, respectively. The obtained Cs 2 NaInCl 6 :Sb and Cs 2 InCl 5 ·H 2 O:Sb exhibit highly luminescent self‐trapped exciton‐related blue (450 nm; photoluminescence quantum yield [PLQY] ≈85%) and yellow (610 nm; PLQY ≈88%) emissions, which are comparable to those obtained by previous methods. Tunable cold/warm white light with a PLQY of up to ≈73% is achieved by the rational assembly of two components with highly overlapped excitation wavelength ranges. Each component demonstrates remarkable stability against humidity and heat. This composite shows great potential in solid‐state lighting for general illumination.