遠端螢光粉LED光學效能提升之研究;Study on improving the optical performance of remote phosphor LED

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题名:	遠端螢光粉LED光學效能提升之研究;Study on improving the optical performance of remote phosphor LED
作者:	周永芳;Chou, Yung-Fang
贡献者:	機械工程學系
关键词:	遠端螢光粉;光學效能;remote phosphor LED
日期:	2019-08-16
上传时间:	2019-09-03 16:38:27 (UTC+8)
出版者:	國立中央大學
摘要:	近年來基於螢光粉轉換的白光LED由於具有長壽命、高可靠性、環境保護、安全性和多種應用領域等許多優點而在LED市場中佔有相當大的比例。但為了滿足可持續發展的要求，持續提高LED的發光效率至關重要。將螢光粉層與LED晶片分離以抑制光線再吸收的遠端螢光粉封裝結構是提高發光效率的有效方法，本文利用次波長結構的抗反射特性設計並製作具有半橢圓球型結構的PET薄膜貼附於遠端螢光粉LED表面以再次提高元件的光取出效率，實驗結果證實在遠端螢光粉LED表面貼附結構周期為350nm且結構高度為300nm橢圓球型結構的PET薄膜，遠端螢光粉LED之光取出效率可提升11.76%。此外，遠端螢光粉LED在貼附具有次波長結構的PET薄膜後，遠端螢光粉LED的色座標、色溫和演色性等顏色特性的變異量皆在量測設備的量測誤差範圍內。在典型的遠端螢光粉白光LED中，螢光粉散射的藍光和螢光粉發射的黃光具有不同的輻射強度分佈。因此，角度顏色分佈變得不均勻，並且會在照射平面中出現不均勻的黃暈現象。本研究中亦經相關實驗證明在遠端螢光粉白光LED中添加TiO2散射粒子提供了一種有效改善的角度色溫均勻性的方法。在螢光粉層中添加重量百分濃度0.2％的TiO2散射粒子和重量百分濃度16.0％的螢光粉經驗證為可獲得較均勻的角度色溫變化與高發光效率和同時維持白光LED整體色溫的最佳參數條件。我們發現與未添加TiO2散射粒子遠端螢光粉LED相比，添加TiO2散射粒子的遠端螢光粉LED的角度色溫均勻性可提高31.82％。在350mA的驅動電流下，相對於未添加散射粒子遠端螢光粉LED，添加TiO2散射粒子的遠端螢光粉LED的光通量增加了8.65％。最後，我們利用實驗驗證將TiO2散射粒子添加到遠端螢光粉白光LED的螢光粉層中並不影響LED元件的可靠度。 ;Recently, white LEDs based on phosphor conversion have accounted for a considerable proportion of the LED market. To meet the requirements of sustainable development, continual enhancement of LED luminous efficiency is crucial. A remote phosphor package is an efficient method for enhancing luminous efficiency. In this study, the light extraction efficiency of a remote phosphor white LED was enhanced using a hemiellipsoidal antireflection subwavelength structure PET film, which was fabricated to reduce the Fresnel reflection of the LED package surface. The completed antireflection subwavelength structure PET film was integrated on the remote phosphor LED surface through a UV-curing adhesive process. The measured results show that the luminous efficiency was enhanced by approximately 11.76% when the ASS film was used. Moreover, the optical properties of color coordinates, color temperature, and color rendering of remote phosphor LEDs were within the measurement error of the measuring equipment when the ASS film was present. However, in typical remote phosphor white LEDs, the phosphor-scattered blue light and phosphor-emitted yellow light have different radiant intensity distributions. Therefore, the angular color distribution becomes non-uniform, and a yellow ring phenomenon appears in the illuminating plane.The utility of low-cost and controllable TiO2 diffuser-loaded encapsulation provided an effective method for improving the angular color uniformity of remote phosphor white LEDs. An inert TiO2 diffuser content of 0.2 wt.% and a phosphor content of 16.0 wt.% in the phosphor layer were determined to be the optimum conditions for obtaining low angular CCT variance, high luminous efficiency, and maintaining the CCT of white LEDs, simultaneously. We found that the angular color uniformity could be improved by 31.82% in the TiO2 diffuser-loaded encapsulation remote phosphor LED, compared with the non-diffuser remote phosphor LED. At a driving current of 350 mA, the luminous flux of the TiO2 diffuser-loaded encapsulation remote phosphor LED was increased by 8.65% relative to the non-diffuser remote phosphor LED. Finally, we showed that incorporating the TiO2 diffuser into the phosphor layer of the remote phosphor white LED did not influence the reliability of the LED.
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