Continuous Ultra‐Broadband Near‐Infrared Sc₂O₃‐Based Nanophosphor Realized by Spectral Bridge of Cr³⁺‐Yb³⁺‐Cr⁴⁺ for Multiple Optical Applications

Abstract

Cr³⁺‐activated near‐infrared (NIR) phosphors are one of the most influential candidates for the new generation of intelligent NIR phosphor‐converted light‐emitting diode (pc‐LED) light sources. For spectral analysis, the broader the spectrum, the more useful information it contains. Herein, ultra‐broadband Cr‐activated Sc₂O₃ nanophosphors, which exhibit NIR ultra‐broadband from 650 to 1600 nm, are developed by the sol–gel method. This ultra‐broadband emission originates from the presence of Cr³⁺ and Cr⁴⁺, two luminescent centers confirmed by diffuse reflection spectra, electron paramagnetic resonance, time‐resolved photoluminescence spectra, and temperature‐dependent emission spectra. The nanophosphor exhibits excellent temperature‐sensing performance with S_A = 4.102% K⁻¹ and S_R = 1.855% K⁻¹. Co‐doping Yb³⁺ into Sc₂O₃ nanophosphors builds the Cr³⁺‐Yb³⁺‐Cr⁴⁺ model to bridge the spectral gap located at 1000 nm, forming a continuous NIR ultra‐broadband spectrum ranging from 650 to 1600 nm for the first time. Moreover, the introduction of Yb³⁺ improves the thermal stability of nanophosphors from 29.49% to 50.65% at 150 °C. The NIR transmission spectra of water, ethanol, and peanut oil demonstrate that Sc₂O₃:Cr³⁺‐Yb³⁺‐Cr⁴⁺ NIR nanophosphors favor potential applications in spectral analysis. The construction of a Cr³⁺‐Yb³⁺‐Cr⁴⁺ spectral bridge for realizing NIR ultra‐broadband phosphors based on cheap blue LEDs provides novel and effective insights.