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 LiInP 2 O 7 : Cr 3+ 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 4 T 2 g → 4 A 2 g transition of Cr 3+ in a single crystal site. To further expand the emission spectrum , Cr 3+ →Yb 3+ energy transfer in LiInP 2 O 7 was designed, and an ultra-broadband emission with a FWHM of 225 nm was obtained through appropriate amount of Yb 3+ 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 LiInP 2 O 7 : Cr 3+ , Yb 3+ phosphor material.