Efficiency optimization of BaY2Al2−yScyGa2SiO12:xCr3+ garnet phosphors with sustained anti-thermal quenching behavior

Abstract

Systematic studies on optimizing the efficiency of garnet phosphors while preserving their anti-thermal quenching behavior remain limited. In this study, we explore the garnet-structured BaY₂Al_2−ySc_yGa₂SiO₁₂:xCr³⁺ phosphor system, emphasizing the critical role of crystal field modulation in achieving this balance. For y = 0, the optimized BaY₂Al_1.95Ga₂SiO₁₂:0.05Cr³⁺ phosphor exhibits broadband deep-red and near-infrared (NIR) emission, with an internal quantum efficiency (IQE) of 73%, an external quantum efficiency (EQE) of 13%, and a luminescence intensity that reaches 108% of its room-temperature value at 150 °C, demonstrating a pronounced anti-thermal quenching behavior. This desired property arises from the thermal population shift of the dominant excited states from the ²E to ⁴T₂ state with increasing temperature. With y > 0, the systematic substitution of Al³⁺ with Sc³⁺ induces greater structural distortion around Cr³⁺ ions, optimizing the crystal field environment, broadening NIR emission, and further enhancing luminescence efficiency. The optimized composition, BaY₂Al_1.5Sc_0.5Ga₂SiO₁₂:0.05Cr³⁺, achieves an impressive IQE of 82%, an EQE of 25% and maintains 104% of its luminescence intensity at 150 °C. A NIR pc-LED with a remarkable output power of 241 mW@300 mA was fabricated using this phosphor, enabling the capture of high-quality finger vein images. This demonstration confirms the feasibility of these phosphors for biometric authentication and other advanced NIR applications.