Sharp-to-Broad Band Energy Transfer in Lithium Aluminate and Gallate Phosphors for SWIR LED

Short-wave infrared (SWIR) phosphor-converted light-emitting diode (LED) technology holds promise for advancing broadband light sources. Despite the potential, limited research has delved into the energy transfer mechanism from sharp-line to broadband emission in SWIR phosphors, which remains underexplored. Herein, we demonstrate bright SWIR phosphors achieved through Cr³⁺/Ni²⁺ energy transfer in LiGa_5(1-Al₅ O₈. High-resolution X-ray diffraction revealed the typical solid solution and distortion occurring in Al³⁺ octahedral sites. In addition, the X-ray absorption spectrum illustrates that Cr³⁺ and Ni²⁺ have different coordination environments, showing the possibility that they occupy different positions or that the coordinated environment of Ni²⁺ is distorted due to charge imbalance. Temperature-dependent studies provide insights into the energy transfer dynamics between Cr³⁺/Ni²⁺, from the ²E level of Cr³⁺ (sharp band) to the ³T₁ level of Ni²⁺ (broadband). The increased emission intensity at lower temperatures in the x = 0.6 and x = 1.0 samples can be explained by the positioning of the ³T₁ level above the ²E level of Cr³⁺ ions. Finally, we established a mechanism involving a sharp line to broadband energy transfer showcasing a high-power SWIR LED with a radiant power of 21.45 mW.