Highly Luminescent Zero-Dimensional Organic Metal (Zn, Mn) Alloyed Halides as Single-Component Yellow Phosphor for White LED Applications

Abstract

Zero-dimensional organic zinc halides have garnered significant attention as efficient and eco-friendly photoluminescent materials. However, its luminance efficiency, which is typically attributed to self-trapped excitons formed within zinc halide tetrahedra, often encounters a serious thermal quenching problem. This issue significantly limits its application in the field of solid-state lighting. Intriguingly, the incorporation of tetra-coordinated Mn²⁺ ions into these organic zinc halides can effectively mitigate unnecessary electron interactions and nonradiative energy transfer between Mn–Mn, achieving significantly improved photoluminescence quantum yield (PLQY) in the alloyed materials. In this work, a series of zero-dimensional Mn²⁺-alloyed 4-benzylpiperidinum zinc chloride hybrids were designed and synthesized by a solvent evaporation method. It is noteworthy that the pure zinc chloride shows a negligible visible emission at 510 nm, whereas (C₁₂H₁₂N)₂Mn_xZn_1–xCl₄ (x = 0.25, 0.5, 0.75, 1) emits visible light ranging from green to yellow at room temperature. Incorporating Mn has led to a remarkable enhancement in PLQY, increasing from a mere 4.02% in the organic zinc halide to an impressive 94.45% in the (C₁₂H₁₂N)₂Mn_0.75Zn_0.25Cl₄. The white LED was successfully fabricated by employing the optimal sample as a single-component yellow phosphor coated on 450 nm chip. The correlated color temperature was determined to be 4770 K with a color rendering index as high as 91. It was also demonstrated with good luminous stability under different working currents. This research provides a straightforward approach for developing eco-friendly, cost-effective, and high-performance single-component yellow phosphors for white LED applications.