倘若發光二極體想要在固態照明上佔有一席之地，白光發光二極體的發光效率就必須有重大的改善。螢光粉轉換的白光發光二極體是產生白色光源最普遍的方法。實驗證明將螢光粉遠離發光二極體的晶粒，可以幫助取出螢光粉的背向散射光子。讓整個螢光粉轉換的白光發光二極體其光輸出與發光效率可以有重大提升。將螢光粉隔開的封裝方式相較於傳統螢光粉轉換之白光發光二極體的封裝方式，在驅動電流350mA的驅動下，每一種光特性都有接近20％的提昇。
將螢光粉隔離的封裝方式有另一個優點，即可以增加螢光粉轉換之白光發光二極體的使用壽命。而且螢光粉轉換之白光發光二極體的相對色溫也會比較穩定。另外，我們的研究發現螢光粉轉換的白光發光二極體有三個可能影響使用壽命的衰退機制，分別是(1) 發光二極體接面處所產生的熱；(2)短波長的光線所造成的傷害；(3)螢光粉的衰退。

The luminous efficiency of white light-emitting diodes (LEDs) must be improved significantly, if LEDs are to become useful for solid-state lighting. The most common method for generating white light source is phosphor-converted white light-emitting diodes (PC-LEDs). It has been demonstrated that by keeping the phosphor layer away from the LED die (the phosphor-on-top package) could extract the phosphor back-scattered photons. And the overall light output and luminous efficiency of PC-LEDs can increase significantly. The improvement of optical characteristics by using the phosphor-on-top package is about 20％ in experiments compared with traditional PC-LEDs (the phosphor-in-cup package), when the PC-LEDs are driven by forward current at 350mA.
And moving the phosphor layer away has an additional advantage of improving life time of PC-LEDs. The phosphor-on-top package exhibits better stability of correlated color temperature than that of the phosphor-in-cup package during the life test. From our study, we presented three degradation mechanisms which affect the long-term performance of PC-LEDs. 1. Junction heat. 2. Short-wavelength emission. 3. Phosphor degradation.

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