Precise Modification of Organic Cations to Enhance the Moisture Stability and Luminescence Efficiency of Mn-Based Halides

Eco-friendly organic-inorganic hybrid metal halides (OIMHs) are widely recognized as promising candidates for next-generation semiconductor materials. However, achieving inherent moisture stability in OIMHs remains a significant challenge due to the highly hygroscopic nature of the halide structures. In response, a strategy to precisely modify the organic cation (18-ACE: 4,13-diaza-18-crown 6-ether) was developed by introducing hydrophobic benzyl groups into 18-ACE, forming a protective layer that enhances the moisture stability of the OIMHs. Specifically, benzyl groups were incorporated into 18-ACE to create 18-ACE-Bn, which was then used as an organic component to construct zero-dimensional Mn-based (18-ACE)MnBr₄ and (18-ACE-Bn)MnBr₄·H₂O, exhibiting photoluminescence quantum yields (PLQYs) of 68.18% and 97.17%, respectively. Notably, (18-ACE-Bn)MnBr₄·H₂O demonstrates exceptional moisture stability compared to (18-ACE)MnBr₄, retaining 97% of its initial PLQY even after 180 days of exposure to 70% relative humidity. Molecular dynamics and density functional theory calculations indicate that this superior stability is attributed to the terminal benzyl groups embedded within the inorganic framework, forming a compact structure with abundant weak interactions. Leveraging the unique spectral characteristics of (18-ACE-Bn)MnBr₄·H₂O, a high-performance WLED with a wide color gamut of 125.2% NTSC (National Television Standard Committee) was developed, highlighting its potential for backlight display applications.