Broad band emission near-infrared material Mg3Ga2GeO8:Cr3+: Substitution of Ga-In, structural modification, luminescence property and application for high efficiency LED

Abstract Series of Cr3+ doped Mg3Ga2GeO8 magnesium gallogermanate near-infrared (NIR) materials were synthesized by solid state method. Mg3Ga2GeO8 with a spinel solid solution structure can provide three different sites for Cr3+, and the priority of Cr3+ entering the three sites has been clearly determined by analyzing the distortions of the three polyhedral sites and local crystal field strength. The emission of the phonon vibration line from the non-forbidden transition 2E→4A2 is observed at T = 10k in sub-peak 1, however, at room temperature, the spectrum presents a broad emission band 700–1200 nm superimposed on 2E→4A2 emission. When introduced In3+ into Mg3Ga2GeO8 to substitute for Ga3+, the emission intensity can be greatly enhanced and a red shift of emission spectra is observed, which may be ascribed to the crystal field environment getting weakened with increasing In3+. A novel NIR phosphor converted light emitting diode was fabricated by combining Mg3Ga1.87In0.1GeO8:0.03Cr3+ with 455 nm blue chip, of which an optical power is 6.143 mW, a photoelectric efficiency is 8.5%, importantly, the spectrum range of device covers 650–1200 nm with a full width at half maximum (FWHM) of 244 nm.