Ce3+,Cr3+ co-doped garnet phosphors with yellow and near-infrared emission for white and near-IR dual-mode pc-LEDs

Abstract

Cr³⁺-activated phosphors with adjustable near-infrared (NIR) emission have attracted considerable attention due to their diverse applications across various fields. While modifying the emission wavelength of Cr³⁺ can be achieved by adjusting its coordination environment, the parity-forbidden d-d transition presents a challenge by limiting absorption and resulting in a low external quantum efficiency (EQE) in Cr³⁺-doped phosphors. Moreover, longer emission wavelengths often coincide with reduced thermal stability. To address these issues, energy transfer from a sensitizer to Cr³⁺ has been proposed as a strategy to enhance both EQE and thermal stability of NIR emission. The selection of an appropriate host structure is crucial. In this study, a garnet structure, Ca₂LuMgScSi₃O₁₂, was identified as a promising candidate for achieving efficient broadband NIR emission under blue light excitation. Specifically, Ca₂LuMgScSi₃O₁₂:Ce³⁺ exhibited a yellow emission with exceptional internal quantum efficiency and EQE of up to 94.6% and 64.8%, respectively. By leveraging efficient energy transfer from Ce³⁺ to Cr³⁺, the Ca₂LuMgScSi₃-O₁₂:Ce³⁺,Cr³⁺ phosphors exhibited tunable yellow to NIR emission. Notable, the highest EQE recorded for Ca₂LuMgScSi₃O₁₂:Ce³⁺,Cr³⁺ was 56.9%, significantly surpassing that of the Cr³⁺ single-doped counterpart. Furthermore, the co-doped phosphor demonstrated thermal stability comparable to that of Ce³⁺ single-doped phosphor. Of particular significance, the developed prototype pc-LED emitted a combination of broadband white and NIR light, demonstrating potential applications in solar-like lighting, food analysis, and biomedical imaging.