Achieving an ultra-broadband infrared emission through efficient energy transfer in LiInP2O7: Cr3+, Yb3+ phosphor

Spectral coverage and saturability within 700–1100 nm of phosphor-converted near infrared light-emitting-diodes (pc-NIR LEDs) are crucial for the practical applications in bioimaging, food quality analysis and night vision fields, while developing ultra-broadband NIR phosphors are still a challenge. Herein, we reported a broadband NIR phosphor LiInP2O7: Cr3+ in phosphate system. The emission spectrum of this phosphor covers 700–1200 nm with a full width at half maximum (FWHM) of 165 nm and an emission peak centering at 860 nm under 460 nm excitation. This broadband emission is verified to be derived from 4T2 g → 4A2 g transition of Cr3+ in a single crystal site. To further expand the emission spectrum, Cr3+→Yb3+ energy transfer in LiInP2O7 was designed, and an ultra-broadband emission with a FWHM of 225 nm was obtained through appropriate amount of Yb3+ codoping. The energy transfer efficiency can reach as high as 81% in this material. Furthermore, the energy transfer mechanism, quantum yield, thermal stability and fabrication performance were investigated in detail, demonstrating the ability of achieving ultra-broadband and efficient NIR emission of LiInP2O7: Cr3+, Yb3+ phosphor material.