研究生: |
許哲瑋 Che-Wei Hsu |
---|---|
論文名稱: |
偏極化白光發光二極體 Polarized White Light Emitting Diodes |
指導教授: |
蘇忠傑
Jung-Chieh Su |
口試委員: |
李奎毅
Kuei-Yi Lee 李志堅 Chih-Chien Lee 楊恆隆 none |
學位類別: |
碩士 Master |
系所名稱: |
電資學院 - 電子工程系 Department of Electronic and Computer Engineering |
論文出版年: | 2010 |
畢業學年度: | 98 |
語文別: | 中文 |
論文頁數: | 81 |
中文關鍵詞: | 偏極化白光發光二極體 、全方位反射器 、次波長光柵 |
外文關鍵詞: | polarized white light LED, omni-directional reflector, subwavelength grating |
相關次數: | 點閱:408 下載:2 |
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本文以具偏光特性之白光發光二極體光源為目標進行各項相關研究,我們選用紫外光晶粒激發螢光粉的方式製作白光發光二極體,其優點為顏色不會隨溫度飄移且演色性高,但缺點為發光效率不高、紫外光外逸。而LED所產生的是非偏極性光,容易造成眩光,使得在應用上有諸多缺點,如應用在室內照明會造成人體感覺不適、在車用照明會造成行車危險等。綜合上述,為了讓白光LED在應用上能夠更具優勢,本文提出一複合光學結構包含「全方位反射器」及「鋁次波長金屬光柵」。全方位反射器可以防止紫外光外漏,並提升LED的發光效率。鋁次波長金屬光柵則用於將具多波長之非偏極性白光轉換成具偏極性白光。
設計製作上,全方位反射器沿用先前研究製作之成品,而鋁次波長金屬光柵透過理論計算找出較佳繞射效率且具可行性之結構參數,接著使用雷射全像顯影術配合反應性離子蝕刻法去製作,所製作出光柵的規格為週期350 nm、厚度為50 nm、空間比為50%,其在可見光波段消光比為1.5。
而將複合光學元件用以封裝白光發光二極體,並以田口式發法調配螢光粉配方,於20 mA的電流驅動下,可得色座標為(0.316, 0.337)、色溫6263 K、演色性96.27,其光源規格已與CIE D65標準光源相當接近。透過頻譜能量強度之量測,全方位反射器能有效阻擋紫外光,且在不傷害電性下增加發光效率32%以上。而鋁次波長金屬光柵可以偏極出射之白光,其消光比為1.52,但會使發光效率降低14%。
This thesis developed a method to generate polarized white light based on exciting multicolor phosphors by ultraviolet (UV) light emitting diode. The advantages of using UV LED generated white light are high color rendering index and wider emission spectrum and the drawbacks are UV leaking and low luminous efficacy.
There are some disadvantages would emerge when LED using in some applications due to LED generate unpolarized light. In interior lighting, glare may cause people uncomfortable. In automobile lighting, glare may increase chance of car accident. For improving these problems, we developed a compound optical element (COE) which combined omni-directional reflector (ODR) with aluminum (Al) subwavelength gratings. Packaged with COE, ODR can solved UV leaking issue and enhance the luminous efficacy. Al gratings can polarize the light passing through it.
In fabrication, ODR had fabricated in previous research. We calculated the parameters of Al subwavelength gratings for achieving better diffraction efficiency in feasible condition. Then, we fabricated Al gratings by laser interference lithography and Reactive Ion Etching. The parameters of the grating, period, thickness, duty ratio, extinction ratio were 350 nm , 50 nm , 50% , 1.5 , respectively.
To packaged white light LED with COE and controlled the composition and concentration of phosphors blend layer by means of Taguchi Method. At a constant applied current of 20 mA, the chromaticity color coordinates, correlated color temperature(CCT), Ra were (0.316, 0.337) , 6263 K and 96.27, respectively. The results were close to that of CIE standard D65 illumination. To measured the spectrum intensity, the ODR packaging structure could enhance the average luminous intensity 32% without any damage on the electronic properties of LED. The Al grating could polarize the white light, the extinction ratio was 1.52,but that would decrease the average luminous intensity 14 %.
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