Valence Conversion to Improve the Ultrabroadband Shortwave Infrared Emission Performance of Cr3+-Doped Olivine-Type Phosphor

Abstract

Broadband near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) have garnered considerable attention across various fields. Nevertheless, the development of long-wavelength NIR phosphors with high efficiency is still hindered. Herein, chromium-doped olivine-type phosphor LiScSiO₄ via a high-temperature solid-state reaction method is successfully synthesized. Under excitation by 470 nm, the as-obtained phosphor exhibits an ultrabroadband shortwave infrared (SWIR) emission centered at 1190 nm with a full-width at half maximum (FWHM) of 325 nm. The SWIR emission intensity is enhanced by controlling the hydrogen atmosphere, which suppresses the formation of Cr⁴⁺ and promotes the transformation of Cr⁴⁺ into Cr³⁺. The internal quantum efficiency (IQE) and absorption efficiency (AE) of LiScSiO₄:Cr³⁺ reach 73.46% and 46.5%, respectively. The Huang–Rhys factor of 11.4 indicates a strong electron-phonon coupling (EPC) effect, contributing to the large FWHM. Finally, encapsulating the as-obtained SWIR phosphors into a prototype pc–LED yields an SWIR output power of 20.07 mW at a driving current of 950 mA, rendering applications for night vision and online detection of water content in alcohol.