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

Cr 3+ -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 Sc 2 O 3 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 Cr 3+ and Cr 4+ , 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 Yb 3+ into Sc 2 O 3 nanophosphors builds the Cr 3+ -Yb 3+ -Cr 4+ 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 Yb 3+ 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 Sc 2 O 3 :Cr 3+ -Yb 3+ -Cr 4+ NIR nanophosphors favor potential applications in spectral analysis. The construction of a Cr 3+ -Yb 3+ -Cr 4+ spectral bridge for realizing NIR ultra-broadband phosphors based on cheap blue LEDs provides novel and effective insights.