Modulating Ultraviolet-Visible-Near Infrared Emission in Hybrid Metal Halides via ns² Ion Doping.

Abstract

Tunable broad-spectrum luminescent materials covering the ultraviolet (UV), visible, and near infrared (NIR) regions are essential for next-generation optoelectronic technologies. However, conventional systems are often limited by inefficient UV emission and the inability to integrate multiple spectral components within a single material. Here, a design strategy that combines ns²-ion with controlled lattice distortion is introduced to overcome these challenges. Using 4,4-difluoropiperidine (DFPD) as the organic cation, a family of hybrid metal halide phosphors, [(DFPD)₂MCl₄·H₂O, M = Cd/Zn] doped with different ns² ion (Sn²⁺, Pb²⁺, Sb³⁺, Bi³⁺, and Te⁴⁺) is synthesized. It is revealed that reduced lattice distortion correlates with enhanced photoluminescence quantum yield (PLQY), enabling broadband self-trapped exciton emission spanning the UV-vis-NIR range within a single host matrix. Leveraging the highly efficient UV emission of 2% Pb-doped (DFPD)₂CdCl₄·H₂O (PLQY: 93%), a high-performance white light emitter with a color rendering index of 92.9 and a correlated color temperature of 6087 K is demonstrated. The materials further exhibit promising functionality in NIR imaging and multi-level anti-counterfeiting. This work elucidates the interplay between lattice distortion and exciton dynamics in Cd/Zn-based hybrid metal halides, providing fundamental insights into their photophysics and establishing a versatile strategy for designing next-generation broadband multifunctional optoelectronic materials.