Improving quantum efficiency and thermal stability of Cr3+-doped olivine solid-solution phosphors with ultra-broadband shortwave infrared emission beyond 1100 nm

Abstract

Broadband shortwave infrared (SWIR) light sources have become increasingly significant in various fields such as industrial monitoring, food testing, biomedical imaging, and environmental sensing. However, creating a reliable and efficient SWIR light sources remains a great challenge. One promising approach involves using SWIR phosphor-converted light emitting diodes (pc-LEDs), which leverage blue LED chips coated with SWIR-emitting phosphors. In this study, we describe a Cr³⁺-doped Li(In_1-xSc_x)GeO₄ olivine solid-solution phosphor that can be excited by blue light to produce broadband SWIR emission. By adjusting the ratio of Sc³⁺ and In³⁺, the peak emission can be tuned from 1115 nm to 1155 nm, while the full width at half-maximum (FWHM) can be modified from 309 nm to 330 nm. The Sc³⁺/In³⁺ ratio is optimized to be 3:17, at which a highest quantum efficiency (IQE) of 28.11% and an improved luminescence thermal stability are achieved. By integrating the title phosphor with a commercial blue InGaN LED chip, a prototype SWIR pc-LED that emit across the 780–1600 nm range with a SWIR output power of 4.4 mW at a driving current of 100 mA and photoconversion efficiency (PCE) of 8.23%@10 mA is fabricated. This work on Cr³⁺-doped olivine solid solution provides a strategy to design efficient SWIR phosphors for solid-state SWIR pc-LEDs and demonstrates potential applications in night-vision and optical imaging.