Efficient Energy Transfer in Te⁴⁺-Doped Cs₂ZrCl₆ Vacancy-Ordered Perovskites and Ultrahigh Moisture Stability via A-Site Rb-Alloying Strategy

As an effective method to improve the optical properties and stability of perovskite matrix, doped halide perovskites have attracted extensive attention in the field of optoelectronic applications. Herein, a series of all inorganic lead-free Te⁴⁺-doped Cs₂ZrCl₆ vacancy-ordered perovskites were successfully synthesized with different Te-doping concentrations by a solvothermal method, and deliberate Te⁴⁺-doping results in green-yellow triplet self-trapped exciton (STE) emission with a high photoluminescence quantum yield (PLQY) of 49.0%. The efficient energy transfer was observed from singlet to triplet emission. Further, the effects of A-site Rb alloying on the optical properties and stability were investigated. We found that A-site Rb alloying and C-site cohalogenation did not change the luminescence properties of Te⁴⁺, but the addition of a small amount of Rb⁺ can improve the PL intensity and moisture stability. Our results provide physical insights into the nS² Te⁴⁺-ion-doping-induced emissive mechanism and shed light on improving the environmental stability for further applications.