Ultra-broadband near infrared phosphor with wide spectral range and long peak wavelength achieved by double-site occupation

Abstract

Near-infrared (NIR) phosphors are key materials for the preparation of NIR phosphor-converted light-emitting diodes (pc-LEDs). However, the development of ultra-broadband, high-efficiency NIR phosphors with a full width at half maximum (FWHM) greater than 200 nm for ultra-broadband long-wavelength emission (above 900 nm) still faces challenges, which hinder their further application. In this study, a series of double perovskite LiYMgWO₆ (LYMW): Cr³⁺ NIR phosphors were prepared using the conventional high-temperature solid-state reaction method. The phosphors exhibit ultra-broadband NIR emission in the wavelength range of 700–1300 nm, with a peak wavelength at 910 nm, a full width at half maximum (FWHM) of 206 nm, and an internal quantum efficiency (IQE) of 48.85 %. The broadband emission consists of two peaks centered at 896 and 996 nm due to the ⁴T₂→ ⁴A₂ transition of Cr³⁺ ions occupying two different six-coordination positions [MgO₆] and [WO₆]. This was confirmed by crystal structure, photo-luminescence spectra and electron paramagnetic resonance spectra. In addition, the sample was combined with a blue LED chip to make a NIR LED device, which successfully demonstrated its application in fields such as night vision and biological tissue penetration.