White Light-Emitting Diodes With High Color Rendering Index and Tunable Color Temperature Fabricated Using Separated Phosphor Layer Structure

In this letter, phosphor-converted white light-emitting diodes (pc-WLEDs) were fabricated using two separated phosphor layers (B&G up/R down) that combine three color phosphors (blue, green, and red) with near-ultraviolet LED chips. The pc-WLEDs have a high color rendering index (CRI) and a tunable color temperature. Regarding the spectra of the phosphors, the CRI value increased with the increasing percentage of overlapping area between the spectra deconvoluted from the electroluminescence spectrum of the pc-WLED. By controlling the thickness of the phosphor layers, the pc-WLEDs with high CRI values and various color temperatures can be obtained. The correlated color temperature and the CRI value of the optimized pc-WLED were 4606 K and 93.8, respectively.