Incorporating rare-Earth terbium(III) ions into $C{s}_{2}AgInC{l}_6$: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 $C{s}_{2}AgInC{l}_6$ NCs to impart and tune the optical performances in the visible light region. $T{b}^{3+}$ ions were incorporated into $C{s}_{2}AgInC{l}_6$ NCs and occupied $I{n}^{3+}$ sites as verified by both crystallographic analyses and first-principles calculations. Trace amounts of Bi doping endowed the characteristic emission (${}^5{D}_4$$\to$${}^7{F}_{6-3}$) of $T{b}^{3+}$ ions with a new excitation peak at 368 nm rather than the single characteristic excitation at 290 nm of $T{b}^{3+}$. By controlling $T{b}^{3+}$ ions concentration, the emission colors of Bi-doped /(Cs_2 Ag(In_{1-x}Tb_x)Cl_6/) NCs could be continuously tuned from green to orange, through the efficient energy-transfer channel from self-trapped excitons to $T{b}^{3+}$ ions. Our study provides the salient features of the material design of lead-free perovskite NCs and to expand their luminescence applications. (© 2020 Wiley‐VCH Verlag GmbH and Co. KGaA, Weinheim)