Competition mechanism of self-trapped excitons and Te⁴⁺ ions emission in the Te⁴⁺ doped vacancy-ordered double perovskite Rb₂HfCl₆ and its excellent properties

Vacancy-ordered double perovskites (VODPs) have attracted much attention because of their excellent photoelectric properties. However, the competition mechanism of self-trapped exciton emission and Te⁴⁺ ion emission in Te⁴⁺-doped VODPs is still unclear. Herein, we synthesized Rb₂HfCl₆ microparticles with a blue self-trapped excitons (STEs) emission, which have a near-unity photoluminescence quantum yield (PLQY), the highest reported value (98.56%) for a VODP matrix. In addition, it has a new broadband yellow emission peak at 560 nm with a PLQY of 76.72% via the equivalent doping of Te⁴⁺ ions. The combination of the blue luminescence of pristine Rb₂HfCl₆ with the yellow luminescence from the Te⁴⁺ ion emission could be used in fluorescence anti-counterfeiting. We also prepared a white light-emitting diode (WLED) with the Commission Internationale de l'Eclairage (CIE) coordinates at (0.3502, 0.3527), a correlated color temperature (CCT) of 4814 K and a color-rendering index (CRI) of 75.3. Moreover, optimized Rb₂HfCl₆:Te⁴⁺ exhibited excellent air and thermal stability. The luminescence dynamics and theoretical calculations jointly reveal that this efficient emission originates from the electron transitions in the different paths. This work provides a new perspective and new theoretical support for the future research on ion-doped luminescent systems.