Ultrabroadband Near‐Infrared Zn 3 Ga 2 GeO 8 :Cr 3+ , Ni 2+ Phosphor for PiG pc‐LED

Abstract Cr 3+ ‐activated broadband near‐infrared (NIR) phosphors are studied extensively for application in phosphor converted light‐emitting diode (pc‐LED), a new light source for substance testing based on NIR spectroscopy. However, the emission of Cr 3+ is mainly located in the NIR I region (700–1000 nm) and many substances show the characteristic spectroscopy in the NIR II region (1000–1700 nm). In this paper, dual‐wavelength emission of NIR I and NIR II is realized in Cr 3+ and Ni 2+ codoped Zn 3 Ga 2 GeO 8 (ZGGO) via energy transfer from NIR I emitting Cr 3+ to NIR II emitting Ni 2+ . The photoluminescent properties of the doped ZGGO are studied as a function of doping concentration and the optimal concentrations of Cr 3+ and Ni 2+ are determined to be 0.04 and 0.003, respectively, with internal quantum efficiency (IQE) of 37.5%. The ZGGO:Cr 3+ , Ni 2+ phosphor‐in‐glass (PiG), is prepared for fabricating PiG‐converted ultrabroadband NIR LEDs to avoid serious reabsorption of the NIR II emission as in the pc‐LED packaged using phosphor dispersed epoxy resin or silicone. The PiG pc‐LED offers photoelectric efficiency of 4.3%@20 mA and NIR output power of 17 mW@200 mA and shows stable spectral distribution against drive current compared to pc‐LED.