Bi³⁺/K-Activated Calcium Lutetium Gallate and the Devices Under UV Chip for Warm WLED and Plant Lighting

Due to indoor agriculture development, blue light is necessary for plant lighting. Here, a blue phosphor, CaLuGaO₄ (CLGO):xBi³⁺ (x = 0.005, 0.0075, 0.01, 0.02, 0.04), has been synthesized using a high-temperature solid-state method. The structure of CaLuGaO₄ is orthorhombic, with a space group Pnma, and Bi³⁺ is doped into the host CaLuGaO₄ to locate the Ca and Lu sites. Under 317 nm excitation, CLGO:Bi³⁺ exhibits a blue broadband emission from 340 to 600 nm. In addition, K⁺ ions are introduced to increase the emission by 1.6 times. Meanwhile, the thermal stability of CLGO:Bi³⁺ and CLGO:Bi³⁺,K⁺ is detected, with 72% of CLGO:Bi³⁺ to 75% for CLGO:Bi³⁺,K⁺. Most importantly, a is 66.11% quantum efficiency is achieved for CLGO:Bi³⁺,K⁺. A blue LED device is fabricated using CLGO:Bi³⁺,K⁺ combined with a 365 nm LED chip, whose blue light matches the absorption spectra of chlorophylls a and b. A warm WLED is also fabricated using the commercial red phosphor CaAlSiN₃:Eu²⁺, the green phosphor (Ba, Sr)₂SiO₄:Eu²⁺, and the blue phosphor CLGO:0.01 Bi³⁺,0.04K⁺ with the CCT of 4679 K and an Ra of 87. All these results indicate that the blue phosphor CLGO:Bi³⁺,K⁺ is an excellent candidate for plant lighting and warm WLED.