Achieving an Improved NIR Performance of Ca_4–xSc_2xZr_1–xGe₃O₁₂:Cr³⁺ via [Sc³⁺-Sc³⁺]→[Ca²⁺-Zr⁴⁺]

High-performance near-infrared (NIR) light sources are highly sought after in advanced spectroscopy techniques, driving the development of NIR phosphor-converted light-emitting diodes (pc-LEDs). Escalating the luminescence intensity and thermal stability of NIR-emitting phosphors, which is a core component of NIR pc-LEDs, is of paramount importance. Herein, chemical unit cosubstitution and cosolvent addition tactics were implemented to simultaneously boost the NIR luminescence performance of the synthesized phosphors. The replacement of [Sc³⁺-Sc³⁺] for [Ca²⁺-Zr⁴⁺] in Ca₄ZrGe₃O₁₂:Cr³⁺ likely reduces the antisite defects and offers a more rigid crystal structure. As a result, the emitting intensity is reinforced significantly, along with a remarkable improvement in thermal stability, acquiring 65% of the initial luminescence at 423 K compared with 42% for the primal sample. Moreover, the introduction of H₃BO₃ further enhances NIR luminescence while maintaining a favorable thermal resistance. The encapsulated NIR pc-LED carries an impressive output power of 71.8 mW at 300 mA and a conversion efficiency up to 15.6% at 10 mA. The practical presentations in food checking, imaging, and detection manifest that Ca_3.5ScZr_0.5Ge₃O₁₂:Cr³⁺,H₃BO₃ is a promising material for spectroscopy-based technologies.