Ultra-broadening near-infrared emission of Cr3+-activated pyroxene phosphors via chemical unit substitution and Yb3+ co-doping

Abstract

Near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) offer distinct advantages over traditional NIR light sources in the miniaturization of spectrometers. Nevertheless, the lack of highly efficient NIR phosphors with a large bandwidth hinders their practical applications. Herein, a novel Cr³⁺-doped (Ca_1−xLi_x)(Mg_1−xSc_x)Si₂O₆ phosphor with a broadened emission has been successfully developed by controlling the lattice disorder via [Li⁺–Sc³⁺] chemical unit substitution in CaMgSi₂O₆:Cr³⁺. Upon exciting the phosphor with 455 nm blue light, (Ca_0.5Li_0.5)(Mg_0.5Sc_0.5)Si₂O₆:4%Cr³⁺ exhibits notable NIR emission centered at approximately 847 nm, featuring a full width at half-maximum (FWHM) of 172 nm. The disordered occupation of Ca²⁺/Li⁺ and Mg²⁺/Sc³⁺ enhances the electron–phonon coupling effect, resulting in a broader emission of (Ca_0.5Li_0.5)(Mg_0.5Sc_0.5)Si₂O₆:Cr³⁺ compared with that of CaMgSi₂O₆:Cr³⁺. In order to further broaden the emission band, an energy transfer (ET) strategy is explored. By leveraging the ET process from Cr³⁺ to Yb³⁺, the FWHM of (Ca_0.5Li_0.5)(Mg_0.5Sc_0.5)Si₂O₆:4%Cr³⁺,0.4%Yb³⁺ is significantly increased up to 264 nm. The phosphor possesses a quantum yield of 46% and a thermal stability of 69% at 423 K. The NIR pc-LED utilizing the (Ca_0.5Li_0.5)(Mg_0.5Sc_0.5)Si₂O₆:Cr³⁺,Yb³⁺ phosphor yields an NIR optical power of 57.31 mW at a driving current of 300 mA, and achieves 10.01% photoelectric conversion efficiency at 25 mA, exhibiting promising potential for application in bio-imaging and food analysis.