Ultra-Broadband and high efficiency Near-Infrared Gd3Zn Ga5-2Ge O12:Cr3+ (x = 0–2.0) garnet phosphors via crystal field engineering

The rapid development of portable spectroscopic detectors has given rise to a great demand for small light sources, and near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) are preferred for their compactness and low cost, while phosphors used in NIR spectroscopy require broadband emission, high quantum yield and good absorption efficiency as well as the spectral range required to achieve detection. Inspired by the tunable structure of Gd3Ga5O12 (GGG), a series of broadband phosphors Gd3ZnxGa5-2xGexO12:1.5%Cr3+ (x = 0–2.0) with continuously tunable emission in the long-wave direction were designed using Zn2+-Ge4+ instead of Ga3+-Ga3+ in GGG to modulate the crystal field environment of Cr3+. The crystal field intensity of the octahedra occupied by Cr3+ decreases with increasing co-substitution, and its full-width at half maximum (FWHM) from 105 nm to a maximum of 211 nm due to the change of local symmetry. In Gd3Zn0.8Ga3.4Ge0.8O12 (GZGG):5%Cr3+, the internal quantum yield (IQY) and external quantum yield (EQY) reaches 79.6% and 31.2% with impressive absorption efficiency (41.1%). The obtained phosphors were made into pc-LED with blue light chips, which was applied to glucose solution degree detection. The results show that the GZGG:Cr3+ will hopefully provide a new strategy for non-destructive testing.