All-inorganic color converter based on a phosphor in bismuthate glass for white laser diode lighting

Abstract

Blue laser diodes (LDs) combined with phosphors have been recognized as the next-generation solid white lighting technology. The phosphor-in-glass (PiG) coating is used for packaging as an appropriate fluorescent conversion material applied to white light LDs. In this work, a low melting point glass Bi₂O₃–B₂O₃–ZnO–BaO (BiBZBa), which was mixed with YAG:Ce³⁺ phosphor powder, was selected as a glass matrix, and the coating of the phosphor in bismuthate glass (PiBG) was successfully fabricated on different substrates through multilayer screen-printing and low-temperature sintering processes. The PiBG-coated substrates were integrated with a 440 nm LD chip in different interlayer structures to obtain PiBG-packaged white laser diodes (WLDs). The thermal performance of Bi₂O₃–B₂O₃–ZnO–BaO glass and the phase composition, microstructure, and luminescence properties of PiBG coatings were studied, and the optical performances of WLDs were investigated. When the reflective WLDs were excited by a blue laser with a laser power density of up to 9.3 W mm⁻², the related luminous flux (LF), luminous efficiency (LE), and chromaticity coordinates were 3091 lm, 103 lm W⁻¹, and (0.32, 0.32), respectively, indicating great potential in PiBG-packaged high power laser lighting applications.