Composite structure Cr:YAG/Ce:YAG and (Ce,Cr):YAG/Ce:YAG transparent ceramics with high color rendering index for white LEDs/LDs

Abstract

Transparent ceramics (TCs) with high color rendering index (CRI) are considered as excellent color converters for white light-emitting diode (LED) and laser diode (LD) devices. In this study, by utilizing the component and structural designs between layers, composite structure (Ce,Cr):YAG/Ce:YAG and Cr:YAG/Ce:YAG TCs with high CRI were fabricated by vacuum sintering. Microstructural and luminescence properties, as well as energy transfer from Ce3+ to Cr3+ ions of as-fabricated TCs were explored systematically. Simultaneously, TC based white LEDs/LDs were assembled via the remote excitation mode. Under 460 nm excitation, a high CRI value of 75.2 was realized in (Ce,Cr):YAG/Ce:YAG TC based white LEDs. As increasing the thickness of the Cr:YAG layer in Cr:YAG/Ce:YAG TC, its red emission intensity could be enhanced distinctly. The optimized CRI and CCT values could reach 74.4 and 4146 K, respectively. In addition, the optimized luminous flux (LF) and CRI of Cr:YAG/Ce:YAG TC based LD device were 160.6 lm and 69.1, respectively. Therefore, the composite structure design is an effective approach to realize the essential promotion of CRI value in TC based white LED/LD devices.