Synthesis of broadband NIR garnet phosphor Ca4ZrGe3O12: Cr3+, Yb3+ for NIR pc-LED applications

Abstract

There are outstanding application prospects for near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) in many fields such as non-destructive detection, bio-imaging, and modern agriculture, in which the development of NIR-emitting phosphors with large full width at half maximum (FWHM), high efficiency, and excellent thermal stability is the challenge of current research. Herein, a broadband NIR-emitting phosphor Ca₄ZrGe₃O₁₂: Cr³⁺ (CZGO: Cr³⁺) was successfully synthesized, which ranged from 650 to 1250 nm with 160 nm FWHM under the excitation of blue light at 477 nm. Based on the first-principles theory calculation, the origination of its matrix luminescence was accurately predicted, and the site-selective occupancy and the formation of various charge transfer bands (CTBs) have also been revealed in detail. With the introduction of Yb³⁺ into CGZO: Cr³⁺, the FWHM was broadened to 230 nm, and the thermal stability was also significantly increased. Furthermore, a NIR pc-LED device was fabricated by combining CZGO: Cr³⁺/Yb³⁺ with a 450 nm commercial LED chip, and it demonstrated satisfactory performance in night vision and bio-imaging.