Study on color-tunable phosphor-coated white light-emitting diodes with high S/P ratios

• Published in: AIP advances 2016-03, Vol.6 (3), p.035127-035127-6
• Main Authors: Guo, Ziquan, Shih, Tienmo, Xiao, Jingjing, Lu, Hongli, Lu, Yijun, Wu, Tingzhu, Lin, Yue, Gao, Yulin, Xiao, Hua, Chen, Zhong
• Format: Article
• Language: English
• Subjects: Color temperature; Light emitting diodes; Nonlinear programming; Organic light emitting diodes; Shape optimization; Spectra; White light
• ISSN: 2158-3226; 2158-3226
• DOI: 10.1063/1.4945387

In this study, we have investigated the trade-off between the color rendering index (CRI, Ra) and the scotopic/photopic ratio (S/P) for color-tunable phosphor-coated white light-emitting diodes (LEDs) at two CRI limitations (Ra ≥ 70 and Ra ≥ 96). First, luminescent spectra measurements have been conducted to determine experimental results of Ra and S/P under various correlated color temperatures (CCTs). Then, a nonlinear programming method has been adopted for the optimization of Ra and S/P by varying spectral shapes through adjusting spectral parameters, such as peak wavelengths, full-width at half-maxima, and relative intensities. Therefore, polynomial curves of optimal S/P versus CCT at two Ra limitations have been discovered, enabling users to obtain optimal S/P under arbitrary CCTs within [2700 K, 6500 K]. In addition, a comparison study between the present work and our previous work has also been conducted at Ra = 70, and a fair agreement of optimal S/P has been observed.