Cr3+-activated Ca2GdZrSnGa3O12 garnet phosphors: structural reconstruction and crystal-field engineered broadband near-infrared emitters for LD/LED-driven light sources

Broadband near-infrared (NIR) phosphor-converted light sources (pc-LSs) are indispensable for emerging technologies that exploit the 700–1100 nm biological transparency window, yet their performance is critically limited by the scarcity of phosphors that simultaneously deliver red-shifted emission, high quantum efficiency, and thermal robustness. Here, we report a Cr³⁺-activated garnet Ca₂GdZrSnGa₃O₁₂ engineered by Ca–Zr/Sn cooperative substitution and M⁵⁺ charge compensation. The incorporation of Cr³⁺ into host lattice with a weak-field octahedral environment produces broadband NIR emission (⁴T₂ → ⁴A₂) centered at 801 nm with bandwidth of 168 nm under 466 nm excitation. M⁵⁺ cations codoping suppresses non-radiative pathways, elevating IQE to 51.58 % and retaining 81.58 % of the room-temperature intensity at 423 K. A low Huang-Rhys factor (S = 0.94) and enlarged activation energy (E_a = 0.25 eV) corroborate the suppressed electron–phonon coupling. Prototype phosphor-converted laser diode (pc-LD) and light-emitting diode (pc-LED) packages deliver optical output powers up to 381.2 mW@1500 mW mm⁻² and 51.2 mW@300 mA with photoelectric conversion efficiencies approaching 25.4 % and 4.48 %, respectively. These findings provide a materials-by-design route that reconciles the long-standing trade-off between spectral red-shift, quantum efficiency, and thermal robustness in Cr³⁺-activated NIR systems, and constitute a decisive advance toward compact, high-power NIR light engines for next-generation photonic applications.