Cr3+-activated NaInSi2O6: An efficient broadband near-infrared phosphor with its applications in LED

A novel near-infrared (NIR) emitting Cr3+-doped clinopyroxene NaInSi2O6 phosphor is designed and synthesized by solid-state method. There are three absorption bands in the NaInSi2O6: 0.04Cr3+ phosphor, peaking at ∼300 nm, ∼470 nm and ∼690 nm, respectively. A broad emission band ranging from 700 nm to 1300 nm is detected at 466 nm excitation, peaking at 936 nm with a full width at half maximum (FWHM) of 151 nm. At the same time, the calculated weak crystal field strength of Cr3+ is 1.93 in the NaInSi2O6 host, resulting in its characteristic broadband emission. Furthermore, the internal quantum efficiency (IQE) and external quantum efficiency (EQE) of NaInSi2O6: 0.04Cr3+ are 68.9% and 27.4%. The integrated emission intensity of NaInSi2O6: 0.04Cr3+ at 423 K retains 55.2% of that at 293 K. By contrast, the NaInSi2O6: 0.04Cr3+-based phosphor-in-glass (PiG) exhibits better thermal stability (64.9%@423 K). A NIR phosphor-converted light emitting diode (pc-LED) was manufactured using a InGaN chip and NaInSi2O6: 0.04Cr3+, presenting the NIR output power of 30.47 mW@200 mA. Used as a NIR light source, the prepared pc-LED shows good promise in the fields of biological tissue imaging and night vision.