Comparative Study of Cr ³⁺ -Activated Garnet Ca ₂ YZnMGe ₃ O ₁₂ (M = Sc, In) Phosphors: Ultraefficient Near-Infrared Luminescence and Structure–Property Relationships

Near-infrared (NIR) phosphor-converted LED (pc-LED) has emerged as a smart light source for multifunctional applications, driving demand for developing high-performance NIR phosphors. However, the design rules for such materials have not been systematically established due to large differences in material systems, compositions, and crystal structures of currently developed materials. Herein, two isostructural and compositionally similar garnet-type phosphors Ca2YZnMGe3O12:Cr3+ (M = Sc, In) were designed and synthesized, which show markedly different performance characteristics, namely, upon 460 nm excitation, the Sc-based garnet achieved an ultrahigh photoluminescence quantum yield (PLQY = 94.0%) and a superior thermal stability (I423 K/I298 K = 81.1%), while the In-base garnet showed a moderate performance (PLQY = 84.8%, I423 K/I298 K = 65.6%), providing an opportunity to reveal the discrepancy in structure and photoluminescence properties via a comparative study. Moreover, an NIR pc-LED device was fabricated by integrating the highly efficient Sc-based garnet with an InGaN LED, which demonstrated excellent performance in information encryption and night vision applications. Therefore, this work not only offers a high-performance NIR phosphor for multifunctional applications but also gives some inspirations for materials design by comparatively analyzing the correlations between structure and properties.