Construction of an Fe–Ni energy bridge for NIR-II luminescence enhancement and anti-thermal quenching via microwave-induced defect engineering

Abstract

Near-infrared (NIR) emitting materials have garnered significant attention due to their exceptional application potential in versatile fields such as phosphor-converted light emitting diodes and food and chemical detection. However, developing a Cr-free NIR phosphor exhibiting an emission wavelength exceeding 1000 nm, along with superior luminescent properties remains a significant challenge. In this work, an Fe³⁺–Ni²⁺ energy bridge was constructed in a Ca₂ScSbO₆ (CSSO) host lattice for the first time. A surprisingly broad-band short-wave NIR emission from Ni²⁺ was demonstrated, enabled by effective energy transfer from Fe³⁺ to Ni²⁺. The NIR emission exhibited a full width at half maximum of 173 nm centered at 1560 nm. The microwave-induced treatment process has notably improved the thermal stability of CSSO:Fe³⁺,Ni²⁺ in the NIR-I and NIR-II regions. At a temperature of 150 °C, thermal stability in the NIR-I region was enhanced to nearly 100%, while in the NIR-II region, it achieved approximately 65% stability. This work not only validates the feasibility of utilizing an Fe³⁺–Ni²⁺ energy bridge to develop broad-band NIR-II luminescent materials, but also presents a strategy for enhancing NIR thermal stability, offering valuable insights for the design of high-thermal-stability NIR-II phosphors.