Cation substitution-dependent phase transforming phosphors: A new alternative broadband NIR-II emitter for solid state lighting

Solid state broadband near-infrared radiation source has great application prospects in the field of agriculture, food and pharmaceutical industries, and health care. Here we report a series of broadband near-infrared luminescent phosphors with the formular of (Zn1−xMgx)Ga2−yO4:yNi (x = 0–1, y = 0.01–0.07) prepared by a high temperature solid-state reaction method. The Zn1−xMgxGa2O4 hosts were first synthesized with different ratios of Zn2+ to Mg2+. A panel of solid-state phosphors were synthesized by Ni2+ doping using a phase transformation method. The resulted phosphors have Ni2+ situated in varied crystal field environment which affected the luminescence behavior of Ni2+. Under the excitation of 365 nm, the phosphors emitted 1000–1600 nm near infrared (NIR) with a broad full width of half maximum (FWHM) of ∼ 250 nm, whose luminescence intensity was highly controllable phase transformation. The phosphor prepared with the optimal host composition and optimized Ni2+ doping concentration had an internal quantum yield of phosphor as high as ∼ 12 %, and its luminescence intensity at 393 K remained 50 % of that at room temperature. The as-prepared optimized phosphor was encapsulated with a 365 nm LED chip to obtain pc-NIR LED device, which emitted broadband NIR. Its application potential in biological imaging was demonstrated.