Study of high CRI white light-emitting diode devices with multi-chromatic phosphor

In this paper, we investigated the connection between the employment of multi-chromatic phosphor and CRI value for WLED devices by simulation, using the excitation and emission spectra of phosphor and surface source property of LED chips acquired from experiments. CRI value was examined in the range of 56.8-76.0 due to the change of phosphor concentration, for traditional blue-pumped yellow phosphor. When red phosphor was added, it was found that as red contents increased, red shift occurred in CIE, and CRI value was enhanced only within a limited range. The highest enhancement in such case was 13.8% for blue-pumped yellow phosphor, and when more multi-chromatic phosphor such as red, yellow, green was mixed, the value of CRI enhancement was 19.2% higher than that of dichromatic LED. Ray tracing simulation revealed that multi-chromatic phosphor also had an impact on luminous efficacy and color temperature for high-power WLED devices. It was also showed in our simulation that CRI value increased with the increase of total phosphor concentration, up until the point of an optimum concentration where CRI value started to decrease. Other parameters such as quantum efficiency and molar absorbance index also contributed to white-LED devices performance. Such simulation results are useful to design the optimum phosphor mixture concentration and are helpful to fabricate high CRI blue-pumped or ultraviolet-pumped WLED devices with the best multi-chromatic phosphor proportion.