Pb²⁺/Mn²⁺ co-doping enables blue-to-white luminescence tuning in Rb₃Cd₂Cl₇ metal halide perovskites

All-inorganic metal halide perovskite materials exhibit high photoluminescence quantum yields (PLQYs), broad emission bands, and tunable luminescence—attributes that confer great potential for white light applications. However, reports on Cd-based perovskites for efficient white light emission remain scarce. Here, the hydrothermal synthesis of Pb2+/Mn2+ co-doped Rb3Cd2Cl7 perovskite crystals, in which the substitutions of Cd2+ by Pb2+ or Mn2+ form the luminescent centers of [PbCl6]4- and [MnCl6]4- for white emission, is reported. Doping with Pb2+ enables a deep-blue emission at 443 nm with anti-thermal quenching and a maximum PLQY of 58.58%, attributed to the formation of confined exciton (CE) around [PbCl6]4-. Concurrently, Mn²⁺ ion doping induces energy transfer toward intrinsic self-trapped exciton (STE) states to [MnCl6]4-, yielding intense yellow emission at 588 nm with a maximum PLQY of 137.79%. This emission is attributed to the intrinsic Cd-related self-trapped excitons (STEs), combined with the generation of local exciton magnetic polarons (LEMPs) through ferromagnetic Mn2+-Mn2+ interactions, via assistance of the coupling with the 245.3 cm⁻¹ phonon mode in Rb3Cd2Cl7: Mn2+. The co-emission of PbCE and LEMP, from the interaction of Pb2+ and Mn2+ centers, achieved a PLQY of 75.4% for white light emission. The phosphor-converted white light-emitting diodes (WLEDs) exhibit an excellent color rendering index (CRI) of 94.1, which is exceptional among recent devices compared to those based on Cd. This underscores its potential for significant applications in the optoelectronic field and offers a new alternative material for perovskite blue and white light-emitting diodes (Pe-LEDs).