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標題: 利用紫外光激發紅綠藍螢光粉進行白光發光二極體之實作研究
Design and Fabrication of White-Light Emitters Using RGB Phosphors Excited by UV LEDs
作者: 沈佳輝
Shen, Chia-Hui
關鍵字: UV-LED
CIE coordinate
conversion efficiency
出版社: 精密工程學系所
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摘要: 摘要 本論文目的在於建立一套有系統的計算方法,改善傳統紫外光發光二極體搭配紅綠藍螢光粉產生白光發光二極體之生產過程中,皆須使用試誤方式來進行色度座標調整的缺陷,利用此有系統的計算方法決定紫外光發光二極體激發紅綠藍螢光粉所呈現的CIE xy座標,可達到加速產品開發時程、減少材料浪費,並降低紫外光之外洩問題。 在本實驗中我們選用波長385 nm之紫外光發光二極體來個別激發紅綠藍螢光粉,實驗出螢光粉比例與激發功率之關係並分析螢光粉的資料數據,推導出其數學關係式並與系統結合。此程式除了可計算CIE xy座標外,也可以由CIE xy座標反推出需要之紅綠藍螢光粉比率。就計算的準確度而言,選擇(0.340,0.350)、(0.200,0.200)、(0.380,0.350)、(0.325,0.275)、(0.300,0.340)等CIE xy座標點,此系統皆能準確預測,xy誤差為±0.01,其範圍在分類區塊之內,證明此計算系統為一可行方法。此外為了要降低紫外光之外洩問題,在紫外光發光二極體搭配紅綠藍螢光粉產生白光發光二極體上塗佈二氧化鈦,以達到吸收多餘未反應之紫外光能量,經由實驗得知其最佳條件為比例4%、厚度為150 um,紫外光外洩將減少83%。本模擬系統所製作之白光LED在工作電流20 mA時轉換效率為3.49 lm/W,因此若要進一步提升效率,則必須由晶片發光效能與螢光粉效率兩方面加以改善。
Abstract Recently, the development of ultraviolet light-emitting diodes (UV-LEDs) to pump red-green-blue (R/G/B) phosphors becomes a promising technique for white LED applications. However, the fabrication process usually needs try-and-error experiments in order to tailor the exact chromaticity coordinate. This thesis has established a computation framework of CIE xy chromaticity coordinate for the white LEDs based on the UV-pumped RGB phosphors. In order to establish the pumping efficiency and emitting spectrum of each phosphor, we have measured the relationship between the excitation power (dominant wavelength: 385 nm) and the phosphor/epoxy mixture ratio. This computation framework can not only predict the CIE xy coordinate but also compute the mixture ratio of the R/G/B phosphors. As a result, an accuracy of 0.01 can be achieved between the simulation and measured data for the following cases: (0.340,0.350), (0.200,0.200), (0.380,0.350), (0.325,0.275), and (0.300,0.340). The results indicate that the developed computation framework can be successfully used to derive the exact chromaticity coordinate of the white LED products. Under a 20-mA injection current, the white LED presents a conversion efficiency of 3.49 lm/W. It could be attributed to the lower efficiency of UV LED chip and the R/G/B phosphors. Finally, to avoid the residual UV radiation emitted from the white LEDs, an experimental work using the TiO2 absorber was performed in the LED package. An optimum condition was obtained where the residual UV radiation can be reduced by 83 % using a 4% TiO2/epoxy overcoat with a thickness of 150 um.
其他識別: U0005-1107200708434300
Appears in Collections:精密工程研究所



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