Insights into a novel garnet-based yellowish-green phosphor: structure, luminescence properties and application for warm white light-emitting diodes

Abstract

White light-emitting diodes (WLEDs) have been considered as the next generation lighting technology due to their advantages such as high efficiency and environmental friendliness. However, current mainstream WLEDs, which are based on blue chips and the Y₃Al₅O₁₂:Ce³⁺ yellow phosphor, suffer from the problem of low color rendering index (CRI). To solve this problem, a yellowish-green phosphor Ca_1.5Y_1.5Al_3.5Si_1.5O₁₂:Ce³⁺ (CYAS:Ce³⁺) based on the garnet structure has been designed in this study. Its crystal structure, band structure, and luminescence properties have been investigated in detail. CYAS:Ce³⁺ exhibits efficient and thermal-stable yellowish-green emission. The 5d centroid shift and crystal splitting of the Ce³⁺ ion in CYAS have been analyzed together with the structure. Moreover, good warm white light with a low correlated color temperature (3210 K), high color rendering index (85.1) and luminous efficacy (88.5 lm W⁻¹) has been obtained by combining CYAS:Ce³⁺ and the red phosphor CaAlSiN₃:Eu²⁺ with a blue LED chip.