利用氧化鋯奈米粒子增進白光發光二極體之色均勻度及發光效率

Abstract

近年來，白光發光二極體發展迅速，其優點為體積小、效率高與節約能源。為加速取代傳統燈源並且廣泛運用於人類生活中，其中提升發光效率與改善均勻性已經成為重要研究議題。目前於工業領域中，最常使用封裝成白光發光二極體之方式為利用藍光晶片搭配黃色螢光粉，其中，傳統點膠方式之最大特點為操作簡單與成本低廉，故成為目前在工業界中最廣泛使用之方法。 雖然傳統點膠方法有許多優點，然而，此白光發光二極體結構卻普遍存在著變角度色溫不均勻之現象，進而導致嚴重黃圈現象。有鑑於此，為解決這個問題，本研究提出利用奈米粒子以改善變角度色溫不均勻之問題，並且可有效提高發光效率。 於本篇論文中，我們使用具有抗熱性、優異耐磨性、與低成本之氧化鋯(Zirconia -ZrO2)奈米粒子，利用摻雜於黃色螢光粉與矽膠中並且搭配藍光晶片所組成的白光發光二極體，透過奈米粒子之高散射能力，使藍光路徑改變，並且改善各角度之色溫均勻性，而此種結構也具有較高之流明輸出。最後，藉由光學模擬軟體分析，證實米氏散射主導整個散射過程，不到1%之氧化鋯奈米粒子用量可提升內部散射強度。故利用摻雜低成本之氧化鋯奈米粒子可取代過多之螢光粉用量，並且可降低白光發光二極體之製造成本。

Recently, the white LEDs (WLEDs) burgeons due to the advantages of small sizes、high efficiency and power saving. To fully substitute the traditional lighting and bring human beings the comprehensive applications, enhancement of luminous efficiency and the improvement of color uniformity have become important issues. WLEDs composed of the blue LED chips and yellow phosphor are most common to use in industry area, among which the traditional dispensing method possess the characteristics of easy packaging and low cost, so this method is adopted universally. In spite of various advantages of tradition dispensing method, structure for this kind of WLEDs still have some problems such as imhomogeneous angular-dependent correlated-color temperature (CCT) , thus the serious yellow-ring phenomenon was unavoidable. To solve this problem, we proposed the utilization of nano-particles to ameliorate the non-uniformity of CCT and further improve the luminous efficiency. In this thesis, the the ZrO2 nano-particle was employed to co-doped with phosphor and silicone encapsulant because of thermal stable、wear-resisting and low cost, via the high scattering effect of nano-particles, blue light emitted from chip was altered significantly, and the angular-dependent CCT uniformity was improved, besides, this structure also provides higher lumen output. Finally, we demonstrate that Mie-scattering dominates the whole scattering process by the analysis of optical simulation software, the capability of scattering was increased with less than 1% ZrO2 usage of nano-particles, hence we can spare the redundant usage of phosphor and make a cost reduction in WLEDs fabrication by doping ZrO2 nano-particles. .