Efficient and Stable Red‐Orange Emission from Polaronic Magnetic Excitons in Mn (II)‐Doped 0D All‐Inorganic Rb4CdCl6

Abstract The impact of magnetic coupling effects on the luminescence of 0D (zero‐dimensional) perovskite materials doped with TM (transition metal) ions remains underexplored. This study synthesizes Mn 2+ ‐doped 0D Rb 4 CdCl 6 halide structures using a solvent‐based method, with Rb + ions systematically arranged around isolated [CdCl 6 ] 4− octahedra. The resulting Rb 4 Cd 1‐ x Mn x Cl 6 powder exhibits stable orange‐red luminescence under UV (ultraviolet) excitation, achieving a PLQY (photoluminescence quantum yield) of 88.96%. The parent Rb 4 CdCl 6 is non‐luminescent, but doping with Mn 2+ induces strong luminescence due to combined emissions from d‐d transitions of Mn 2+ , weakly ferromagnetically coupled Mn 2+ pairs, and STEs (self‐trapped excitons). Characterization via XRD (X‐ray diffraction) and DFT (density functional theory) reveals that Mn 2+ doping occurs through both substitutional and interstitial processes, facilitating magnetic coupling. Raman spectroscopy identifies strong electron‐phonon coupling at a phonon mode of 112 cm −1 , supporting STEs generation. Magnetic property analysis shows significant ferromagnetic coupling between Mn 2+ pairs and paramagnetic single Mn 2+ ions, enhancing luminescence. The material demonstrates remarkable structural and thermal stability, positioning Rb 4 Cd 1‐ x Mn x Cl 6 as a promising candidate for optoelectronic applications.