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 Mn2+‐doped 0D Rb4CdCl6 halide structures using a solvent‐based method, with Rb+ ions systematically arranged around isolated [CdCl6]4− octahedra. The resulting Rb4Cd1‐xMnxCl6 powder exhibits stable orange‐red luminescence under UV (ultraviolet) excitation, achieving a PLQY (photoluminescence quantum yield) of 88.96%. The parent Rb4CdCl6 is non‐luminescent, but doping with Mn2+ induces strong luminescence due to combined emissions from d‐d transitions of Mn2+, weakly ferromagnetically coupled Mn2+ pairs, and STEs (self‐trapped excitons). Characterization via XRD (X‐ray diffraction) and DFT (density functional theory) reveals that Mn2+ 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 Mn2+ pairs and paramagnetic single Mn2+ ions, enhancing luminescence. The material demonstrates remarkable structural and thermal stability, positioning Rb4Cd1‐xMnxCl6 as a promising candidate for optoelectronic applications.