Incorporating Rare‐Earth Terbium(III) Ions into Cs₂AgInCl₆:Bi Nanocrystals toward Tunable Photoluminescence

The incorporation of impurity ions or doping is a promising method for controlling the electronic and optical properties and the structural stability of halide perovskite nanocrystals (NCs). Herein, we establish relationships between rare-earth ions doping and intrinsic emission of lead-free double perovskite Cs₂ AgInCl₆ NCs to impart and tune the optical performances in the visible light region. Tb³⁺ ions were incorporated into Cs₂ AgInCl₆ NCs and occupied In³⁺ sites as verified by both crystallographic analyses and first-principles calculations. Trace amounts of Bi doping endowed the characteristic emission (⁵ D₄ →⁷ F_6-3 ) of Tb³⁺ ions with a new excitation peak at 368 nm rather than the single characteristic excitation at 290 nm of Tb³⁺ . By controlling Tb³⁺ ions concentration, the emission colors of Bi-doped Cs₂ Ag(In_1-x Tb_x )Cl₆ NCs could be continuously tuned from green to orange, through the efficient energy-transfer channel from self-trapped excitons to Tb³⁺ ions. Our study provides the salient features of the material design of lead-free perovskite NCs and to expand their luminescence applications.