Enhanced Ambient-Air, Thermal, and Photostability of Green-Emitting (PPIP)2MnCl4 for White LEDs and X-ray Imaging

Abstract Zero-dimensional (0D) organic–inorganic metal halides (OIMHs) are highly promising lead-free luminescent materials. However, their inherent instability severely limits their long-term applications. Herein, a relatively stable zero-dimensional manganese halide, (PPIP)2MnCl4, was synthesized. In this structure, PPIP+ cations establish an extensive hydrogen-bond network with [MnCl4]2– tetrahedra, significantly enhancing both the material’s luminescent properties and environmental stability. (PPIP)2MnCl4 exhibits bright green luminescence at a wavelength of 539 nm, with a full width at half-maximum (fwhm) of 60 nm and a photoluminescence quantum yield (PLQY) of 97.2%. Notably, the material retains its luminescent characteristics even after storage in ambient air for 25 days, as well as after thermal treatment and photoirradiation. Two WLEDs were fabricated using K2SiF6:Mn4+ and CaAlSiN3:Eu2+ red phosphors, respectively, demonstrating their potential for white-light illumination. As an X-ray scintillator, (PPIP)2MnCl4 achieves a light yield of 27,511 photons/MeV, with a detection limit as low as 319.8 nGy/s, enabling high-resolution imaging at a spatial resolution of 9.68 lp/mm. These results indicate that (PPIP)2MnCl4 is a highly promising candidate material for next-generation solid-state lighting and high-resolution X-ray imaging.