Efficient ultra-broadband NIR-II emission achieved by multi-site occupancy in Mg3Ga2GeO8: Ni2+ phosphor

It is an important and urgent task to improve the luminous efficiency and emission bandwidth of existing luminescent materials with emission in near infrared (NIR) spectral region (especially for NIR-II spectral region from 1000 to 1700 nm). Herein, we report a novel Ni ²⁺ doped phosphor Mg ₃Ga ₂GeO ₈: 0.8 %Ni ²⁺ which exhibits ultra-broadband emission (from 1100 to 1700 nm, the full width at half maximum (FWHM) is up to 300 nm) with high quantum efficiency (The internal quantum efficiency (36.7 %) and external quantum efficiency (7.3 %) are relatively high in the reported Ni ²⁺ dope NIR-II emitting phosphors). The phosphor presents desirable thermal stability of luminescence (At 373 K, it remains 56.2 % of the initial intensity at room temperature). This work not only provides an advanced NIR-II emitting phosphor which can be effectively pumped by commercial near ultraviolet light emitting diode chips, but also introduces a new strategy (that is to explore a suitable host in which there exists many different crystalline sites for the occupation of activators) for the exploration of efficient ultra-broadband NIR-II emitting phosphors.