Highly efficient and stable near-infrared broadband luminescence in SrGa4O7:Cr3+, Yb3+ phosphor

Abstract

Developing novel broadband near-infrared (NIR) phosphors is crucial to promote NIR phosphor-converted light emitting diodes (pc-LEDs) development. In this paper, a novel multifunctional near-infrared phosphor, SrGa4O7:Cr3+, Yb3+, was synthesized by the conventional high-temperature solid-state method. The emission band of the material spans from 650 nm to 1100 nm. Despite the predominance of four-coordinate and five-coordinate sites within the SrGa4O7 (SGO) lattice, the incorporation of Cr3+ ions induces distortion in the Ga–O tetrahedra, resulting in an octahedral environment for Cr3+. Under blue light excitation, the Cr3+ ions exhibit an ultra-wide emission band (650–900 nm) with a Full Width at Half Maximum (FWHM) of 131 nm. Furthermore, energy transfer from Cr3+ to Yb3+ was achieved in SrGa4O7:Cr3+, Yb3+, and the incorporation of an optimal quantity of Yb3+ co-dopant yielded a significantly enhanced and extraordinarily broad spectrum from 600 to 1100 nm. Moreover, Yb3+-codoping improves the thermal stability due to the energy transfer from Cr3+ to more thermally stable Yb3+ emitters, and the integrated intensity of SrGa4O7:Cr3+, Yb3+ at 300 K was 74% of that at room temperature. Based on these findings, a blue-light-excited NIR pc-LED was encapsulated. The forward voltage and intensity of the LED remained almost constant after 500 h of thermal aging at high temperatures, indicating its particular reliability in NIR pc-LED applications. The results show that SrGa4O7:Cr3+, Yb3+ phosphors have great potential in ultra-wideband NIR pc-LED applications.