Insight into a Novel Garnet-based Yellowish-green Phosphor: Structure, Luminescence Properties and Application for Warm White Light-emitting Diodes

White light-emitting diodes (WLEDs) have been considered as the next generation lighting technology due to its advantages such as high efficiency and environmental friendliness. However, current mainstream WLEDs, which is based on blue chip and Y3Al5O12:Ce3+ yellow phosphor, suffer from the problem of low color rendering index (CRI). To solve this problem, a yellowish-green phosphor Ca1.5Y1.5Al3.5Si1.5O12:Ce3+ (CYAS:Ce3+) based on garnet structure has been designed in this study. The crystal structure, band structure, luminescence properties have been investigated in detail. The CYAS:Ce3+ exhibits efficient and thermal-stable yellowish-green emission. The 5d centroid shift and crystal splitting of Ce3+ ion in CYAS has been analyzed together with the structure. Moreover, good warm white light with low correlated color temperature (3210 K),high color render index (85.1) and luminous efficacy (88.5 lm/W) has been obtained by combing the CYAS:Ce3+, red phosphor CaAlSiN3:Eu2+ with blue LED chip.