title: Effects of phosphor distribution and step-index remote configuration on the performance of white light-emitting diodes.
abstract: Phosphor-converted white light-emitting diodes (pc-WLEDs) are fabricated by combining CaSi2O2N2:Eu2+ and Ca2Si5N8:Eu2+ phosphors with a blue chip. Experimental results demonstrate that placing the red phosphor layer above the yellow one (Y down/R up) yields the highest luminous efficiency, making it the preferable phosphor distribution for pc-WLEDs rather than Y up/R down. This finding suggests that the extent of overlap between the emission spectrum of short-emission-wavelength phosphors and the excitation spectrum of long-emission-wavelength phosphors and their luminous efficacy of radiation should be taken into account simultaneously when studying the optical characteristics of pc-WLEDs. Compared to common pc-WLEDs with silicone gel as the remote layer, the proposed step-index remote configuration exhibits superior luminous efficiency because of reduced total internal reflection and Fresnel loss.
authors.forename: Chung-Hao
authors.initials: CH
authors.lastname: Chiang
authors.forename: Hung-Yi
authors.initials: HY
authors.lastname: Tsai
authors.forename: Ting-Shi
authors.initials: TS
authors.lastname: Zhan
authors.forename: Han-Yu
authors.initials: HY
authors.lastname: Lin
authors.forename: Ying-Chien
authors.initials: YC
authors.lastname: Fang
authors.forename: Sheng-Yuan
authors.initials: SY
authors.lastname: Chu