CaLuGaO4: Bi3+, Al3+ blue phosphor with excellent thermal stability for multiple LED applications

Abstract

The development of Bi3+-doped phosphors with outstanding luminescent properties is imperative due to their promising prospects for applications in near-ultraviolet LEDs. In this study, we have successfully obtained a high-quality Bi3+-doped CaLuGaO4 blue phosphor via high temperature solid-phase method. Bi3+ is found to substitute for both Ca2+ and Lu3+ sites within the crystal lattice, leading to a photoluminescence excitation spectrum that prominently displays two peaks at 335 nm and 370 nm, respectively. These peaks are well-aligned with the near-ultraviolet LED chips. Significantly, the CaLuGaO4: 0.004Bi3+ exhibits outstanding luminescent thermal stability, with the luminescence intensity at 420 K retaining a remarkable 76.7% of its value at 90 K. It is noteworthy that the luminescence intensity and thermal stability can be further enhanced through the incorporation of Al3+. The modified CaLuGa0.7Al0.3O4: 0.004Bi3+ phosphor exhibits exceptional performance, with its integrated emission intensity at 420 K reaching 91.8% of the room temperature value and an internal quantum efficiency of 60.8%. The PL spectra of CaLuGaO4: Bi3+ is found to match well with the blue regions of the absorption spectra for chlorophyll a and b, making it a viable candidate for applications in plant growth lighting. In addition, by combining CaLuGaO4: Bi3+ with commercial red and green phosphors and utilizing 365 nm LED chips, a series of high-quality white light emitting diodes (w-LEDs) have been successfully produced. These w-LEDs boast a color rendering index (CRI) that exceeds 90, indicating a promising prospect of CaLuGaO4: Bi3+ phosphors in the development of high-quality w-LEDs powered by ultraviolet chips.