Ag Doping Triggered Electronic Structural Engineering in Halide Quadruple Perovskite Toward Near-Unity Luminescence Quantum Yield

Ion doping is an effective strategy to regulate the optical performance in metal halide perovskites for desirable light emission manipulations. In this work, a Mn 2+ and Ag + co-doping strategy is utilized to improve the luminescence in Cs 4 CdBi 2 Cl 12 quadruple perovskite. Mn 2+ and Ag + ions are proven to be incorporated into Cs 4 CdBi 2 Cl 12 lattice. Mn 2+ ions occupy Cd 2+ sites and Ag + ions occupy Cd 2+ sites or vacancies. The alloyed Mn 2+ ions bring efficient orange-red luminescence attributed to the energy transfer process from the host to Mn 2+ ions. A small amount of Ag + doping can optimize the band structure and increase the exciton binding energy, thus promoting efficient radiative recombination from d–d transition of Mn 2+ ions and boosting the PLQY up to 94.6%. Furthermore, Cs 4 Cd 0.75 Mn 0.25 Bi 2 Cl 12 :1.5%Ag + show good phase and emission stability in ambient environment and is employed in white light-emitting diodes with commercial blue and green phosphors on a near-ultraviolet LED chip. This work provides insights for understanding the composition-structure-property relationship in vacancy-ordered quadruple perovskites and designing highly efficient luminescent lead-free metal halides for solid-state light emitting applications.