Smaller Stokes Shift Induced Highly Efficient Broadband Near Infrared Garnet Phosphor

Broadband near-infrared (NIR) phosphor converted light emitting diodes (pc-LEDs) are novel compact light sources that enable portable devices for substance detection. However, to achieve such efficient pc-LEDs is still a challenge due to lack of efficient phosphors. In this paper, Stokes shift as an efficiency predictor is emphasized. In Cr3+ activated Ca2LuZr2Al3O12 (CLZA) garnet phosphor, Stokes shift decreases from 2990 to 2854 cm(-1) upon substituting Ca-Zr with Lu-Al. As a result, electron-phonon coupling related nonradiative process is reduced. The external quantum efficiency is significantly enhanced to 47.4%, and the as fabricated NIR pc-LED offers 33.7% @10 mA electro-optical efficiency. The results can advance the development of efficient NIR phosphors.

Automated summary

This paper investigates a novel compact light source, broadband near-infrared phosphor converted LED (pc-LED), and addresses the challenge of lacking efficient phosphors. By introducing the concept of external quantum efficiency through Stokes shift, the efficiency of the light source is significantly improved.