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  • 學位論文

利用奈米壓印技術與表面微透鏡結構增進白光固態照明元件效率之研究

Using nanoimprint techniques and micro-lens structures to improve the efficiency of white-light solid-state lightening devices

指導教授 : 陳學禮

摘要


在本論文中,將針對影響螢光轉換型白光固態照明元件效率的因素進行探討,其中由於此種白光固態照明元件的特性,我們可以將元件的發光效率分為兩大部分來討論。第一部分是底部用來激發黃光的藍光發光二極體之光萃取效率;而第二個部分則為螢光粉封裝層的螢光轉換效率。 在第一個部份的論文中,我們透過有限時域差分法 (Finite-Difference Time Domain;FDTD) 計算具有表面微透鏡結構的藍光發光二極體之光萃取效率,透過計算其離開氮化鎵的光能量流來分析點光源在透鏡下方不同相對位置時之出光行為。由研究中可以發現最密堆積的微透鏡結構會使得點光源在透鏡相切處下方的出光受到大幅的抑制,主要原因為點光源在此處發光將使得大部分的光變成已相當大的斜角入射氮化鎵與空氣表面而造成出光的下降,因此非最密堆積的微透鏡陣列將會具有較佳的光萃取效率。調整適當的週期與曲率半徑,其整體光萃取效率將具有平的LED元件光萃取效率四倍以上之效果。 在第二個部份的論文中,我們應用奈米壓印技術以及光學薄膜技術來改善螢光轉換型白光發光二極體中螢光封裝層的轉換效率。首先透過嚴格耦合波分析法 (Rigurous Coupled-Wave Analysis;RCWA) 來分析計算不同週期性奈米尺寸結構的光萃取效率。由研究中可以發現具有適當週期深度的反圓錐結構有最佳的光萃取效率,可藉由降低臨界角內反射以及透過遶射的方式將臨界角外的光繞射到空氣中而出光。我們透過奈米壓印技術成功的在螢光封裝層表面製作藍光最佳以及黃光最佳兩種參數的反圓錐結構,並在封裝層底部鍍上具有藍光波長450nm下高穿透、黃光波長570nm下高反射的光學薄膜以降低重新入射回藍光LED或者側壁所造成的損耗。若同時考慮光萃取效率以及藍光黃光之間的螢光轉換效率,具有最佳黃光出光的結構搭配底部光學薄膜對於螢光轉換型白光發光二極體來講為最適當的結構。未來將繼續針對具有此種結構的白光LED的演色性以及色溫、色度上進行更進一步的探討。

並列摘要


Improving the efficiency of the light-emitting diodes (LED) is one of the important issues for the incoming energy shortage. In this thesis, we studied the factors that influence the efficiency of phosphor-converted white-light solid-state lightening device. There were two things we need to consider : first, the extraction efficiency of the pumping blue light-emitting diode and second, the conversion efficiency of phosphor. In the first part of this thesis, the extraction efficiency improvement of the blue LED with surface micro-lens arrays was analyzed by Finite-Difference Time Domain (FDTD) method. The extraction behaviors of point light sources at different relative position were also studied by computing the power flux that leaves the GaN and air interface.We found the optimal structure is the non-closed packed micro-lens array because the extraction will be decreased dramatically by changing the light emission direction to the oblique direction when the point source is at the position below the tangent between two closed-packed lens. We also found that the extraction efficiency of micro-lens array with optimal period and radius of curvature can be enhanced more than 4 times than planar blue light-emitting diodes. In the second part of this thesis, the nanoimprint techniques and optical thin films were applied in the phosphor encapsulation to improve the conversion efficiency of the phosphor-converted LED. The extraction efficiency of various periodic nano-scale structures were first analyzed by Rigurous Coupled-Wave Analysis (RCWA) method. We found the best structure is inverse cone with optimal period and depth, which can increase the transmittion due to elimination of reflection and diffractive transmittion when the angle of incidence is more than critical angle. We successfully fabricated two kind of the inverse cone structure on the front surface of the phosphor encapsulation by nanoimprint techniques. The optical thin films with high transmittance at wavelength 450nm and high reflectance at wavelength 570nm were also deposited at the backside surface of the phosphor encapsulation to reduce the absorption loss when the light incident to blue-LED or the sidewall of device. Considering the conversion between blue light and yellow light, the best structure was the combination of the inverse cone with highest yellow light extraction efficiency and optical thin films. More details about the colour temperature and colour-rendering index of the phosphor-converted white-light LED will be studied in the future.

參考文獻


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被引用紀錄


方程毅(2012)。介電奈米粒子與氧化金之光學性質探討及其在光電元件上之應用〔博士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2012.01880
盧泰言(2012)。液態反射鏡與碳化矽基材在高靈敏度感測元件及高功率發光二極體應用之研究〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2012.01652

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