Blue light-excited broadband NIR-II-emitting Li2ZnSn3O8:Cr3+,Ni2+ phosphor for multifunctional optical applications

Abstract

The second near-infrared window (NIR-II, 1000–1700 nm) emitting phosphor is a key component for the phosphor-converted light-emitting diode (pc-LED), which has garnered significant attention. However, it remains a major challenge to discover efficient NIR-II broadband phosphors that can be excited by blue LEDs. Herein, Cr³⁺ and Ni²⁺ ions were co-doped into the Li₂ZnSn₃O₈ (LZSO) host. LZSO:Cr³⁺,Ni²⁺ phosphor achieves a broadband NIR-II emission peak at 1465 nm with a large full width at half maximum (FWHM) of 300 nm and internal quantum efficiency (IQE) of 43.31% under excitation at 426 nm because of the efficient energy transfer (ET) from Cr³⁺ to Ni²⁺. In addition, a dual-emissive doped phosphor across the NIR-I (700–1000 nm) and NIR-II regions with a higher sensitivity at physiological temperatures was obtained. The relative sensitivity value (S_r) reaches 1.44% K⁻¹ at 293 K, indicating that the LZSO:Cr³⁺,Ni²⁺ phosphor is a potential candidate for NIR optical thermometers in biotechnological applications. The manufactured NIR-II pc LED provides a radiative flux of 8.26 mW with a photoelectric conversion efficiency of 2.71% at a drive current of 100 mA and has promising potential in night vision, medical imaging, and spectral analysis applications.