Six- and five-coordinated Cr3+ in Ga2GeO5 invokes tunable broadband near-infrared emission toward night-vision applications

Broadband near-infrared (NIR) light sources play a critical role in widespread applications such as advanced spectroscopy analysis and nondestructive testing. One of the most promising techniques is the fabrication of broadband NIR phosphor-converted light emitting diode (pc-LED). However, the purposeful design of a tunable ultra-broadband NIR-emitting phosphor in a single host is still a challenge. In this work, Ga2GeO5 with two sites of six-coordinated [Ga1O(6)] and five-coordinated [Ga2O5] is chosen to host Cr3+, successfully producing tunable broadband NIR luminescence (680-1350 nm). It can be tuned largely from 828 to 970 nm with the full-width at half maximum (FWHM) varied from 208 to 258 nm just by simply adjusting the Cr3+-doping content. The tailoring of the Cr3+ NIR spectral emission is ascertained to the site occupation preference and competition. The encapsulation of a prototype of NIR pc-LED with an output power of 29.5 mW@390 mA is conducted for the implementation of night-vision application. This work provides a novel broadband NIR phosphor by Cr3+-doping in both the six- and five-coordination field, meanwhile, further demonstrating the feasibility of discovering new host material with more than one crystallographic site for Cr3+ to trigger tunable broadband NIR emission.

Automated summary

Broadband near-infrared (NIR) light sources are crucial for advanced spectroscopy and nondestructive testing. This study successfully designed a tunable ultra-broadband NIR-emitting phosphor by adjusting the doping content of Cr3+ in Ga2GeO5, demonstrating the feasibility of discovering new host materials with multiple crystallographic sites to trigger tunable broadband NIR emission. The findings have significant implications for the development of versatile NIR light sources.