Constructing Broadband Near‐Infrared Garnet Emitters CaGd₂Ga₄SiO₁₂:Cr³⁺ with Unity Quantum Efficiency and High Thermal Stability for Versatile Applications

The pursuit of broadband near-infrared (NIR) phosphors for next-generation smart NIR light sources has garnered extensive interest. However, developing phosphors efficiently excitable by blue light to produce thermally stable and highly efficient broadband NIR emission surpassing 830 nm remains a formidable challenge. Herein, a novel CaGd₂Ga₄SiO₁₂ garnet is reported, designed through a structure reconstruction approach to host Cr³⁺ ions for developing a high-performance broadband NIR phosphor. By strategically introducing Jahn-Teller distortion at the octahedral sites via chemical pressure, Cr³⁺ is endowed with a super-broadband NIR emission spanning 600-1300 nm centered at 837 nm. The full-width at half maximum (FWHM) varies from 187 to 223 nm across Cr³⁺ doping concentrations, with the highest internal quantum efficiency (IQE) of 99.01%. Remarkable luminescence thermal stability (90.37%@423 K) is bolstered by a weak electron-phonon coupling (EPC) effect and trap-mediated energy compensation, a result of the heterovalent ion substitutions in dodecahedral and tetrahedral sites. Furthermore, a prototype broadband NIR phosphor-converted light-emitting diode (pc-LED) is fabricated, delivering a substantial NIR output power of 287.7 mW at 1100 mA and a power conversion efficiency (PCE) of 24.4% at 30 mA, enabling impressive performance in versatile applications, including component analysis, non-destructive testing, NIR imaging, and night vision.