Dual-Band-Tunable White-Light Emission from Bi³⁺ /Te⁴⁺ Emitters in Perovskite-Derivative Cs₂ SnCl₆ Microcrystals

Luminescent metal halides have attracted considerable attention in next-generation solid-state lighting because of their superior optical properties and easy solution processibility. Herein, we report a new class of highly efficient and dual-band-tunable white-light emitters based on Bi³⁺ /Te⁴⁺ co-doped perovskite derivative Cs₂ SnCl₆ microcrystals. Owing to the strong electron-phonon coupling and efficient energy transfer from Bi³⁺ to Te⁴⁺ , the microcrystals exhibited broad dual-band white-light emission originating from the inter-configurational ³ P_0,1 →¹ S₀ transitions of Bi³⁺ and Te⁴⁺ , with good stability and a high photoluminescence (PL) quantum yield of up to 68.3 %. Specifically, a remarkable transition in Bi³⁺ -PL lifetime from milliseconds at 10 K to microseconds at 300 K was observed, as solid evidence for the isolated Bi³⁺ emission. These findings provide not only new insights into the excited-state dynamics of Bi³⁺ and Te⁴⁺ in Cs₂ SnCl₆ , but also a general approach to achieve single-composition white-light emitters based on lead-free metal halides through ns² -metal ion co-doping.