Improvement of Luminous Efficiency in White Light Emitting Diodes by Reducing a Forward-bias Voltage

Yukio Narukawa, Masahiko Sano, Masatsugu Ichikawa, Shunsuke Minato, Takahiko Sakamoto, Takao Yamada, Takashi Mukai
2007 Japanese Journal of Applied Physics  
A packaging scheme utilizing omni-directional reflective (ODR) optical coating is described to enhance the light extraction of near UV excited, phosphor-converted LEDs. A simple 1D model was developed to analyze the spectra of the extracted light measured with an integrationsphere as a function of phosphor layer concentration and thickness. Quantitative determination of the absorption coefficients at the pump and fluorescent light wavelength along with the conversion coefficient of phosphors
more » ... e obtained. The reflection of the ODR film and the back reflector are also characterized. These parameters are then used for efficiency optimization of the present packaging scheme. A maximum enhancement of 40% can be expected with the materials and the configuration used in the present work.
doi:10.1143/jjap.46.l963 fatcat:c3el4rv6qzh5lkmlh5fmz4ymhy