利用前瞻量子點於發光二極體之照明與顯示器應用

Abstract

發光二極體具有省電、體積小、發光效率高、壽命長等優點，因此逐步取代傳統發光燈源，成為新一代顯示器背光主要光源。現今的顯示器多以藍光發光二極體搭配黃色螢光粉做為白光背光源，但有色彩飽和與鮮豔度不佳的問題。目前最具潛力的量子點螢光材料，擁有極窄的發光半高寬，並具有發光波長能隨粒子大小變化而改變的優點使得量子點發光二極體可以達到接近連續光譜、高演色性的特性。於本論文中，我們利用量子點螢光材料製作具有廣色域與高飽和度的高光品質發光二極體作為顯示器的背光源。論文將分為兩部分，分別討論色穩定度大幅提升的量子點顯示器背光模組及可獨立調控的量子點微顯示器。 第一部分將針對如何維持高發光效率的量子點發光二極體做研究。一般而言，當量子點螢光粉受熱造成分散劑揮發或受到氧化時，會產生自聚集、波長紅移與螢光共振能量轉移(FRET)現象，造成發光效率降低。當量子點懸浮於分散劑中擁有最佳發光效率，因此我們將液狀之量子點螢光粉封裝於高透光度石英盒中，以隔絕熱與環境中濕氣與氧氣，使量子點螢光粉可維持最佳發光效率。經過一千小時信賴性測試之後，傳統量子點封裝方式發光效率下降約73%，而利用高透光度石英盒保護量子點螢光粉之封裝方式發光效率僅下降約13%，本研究成功解決傳統量子點封裝無法維持長時間有效發光之缺點，並且可將以種封裝方式應用於顯示器背光光源之中，以提升其發光效率。 於第二部分研究中，由於傳統液晶顯示器顯示反應速率相較於LED慢，且當背光經過模組與濾光片時，有極大部分之光被吸收，造成能量損耗。因此本研究利用霧化噴塗系統噴塗紅、綠、藍三色量子點於可單獨操控點亮之微發光二極體陣列上，製做出可直接顯示出光之微米顯示器，不僅可大幅縮短反應時間並且增加光的利用率，此種顯示器不需要藉由液晶來調控畫面的明亮度，因此也可以大幅減少顯示器的厚度。此外，透過紅、綠、藍量子點所製作的白光微顯示器可大幅的提升顯示器的色域，使色域達到NTSC 152 %的卓越表現可提供更生動、飽和的色彩，此種量子點微顯示器未來極有潛力可應用於穿戴式裝置之顯示器。

Light-emitting diodes (LEDs) have gradually replaced traditional lighting and become a new generation of display backlight source due to the advantages of low power consumption, small size, high luminous efficiency, long life, etc. Nowadays, most of displays fabricate white backlight sources by the use of blue light-emitting diodes and yellow phosphors, which have some problems such as the lower color saturation and poor brightness. However, the most potential fluorescent material: quantum dots have played a critical role in advanced display system due to its extremely narrow emitting FWHM, and the wavelength bandgap variation by the tunable of the particle size. As the result, quantum dot display can provide great characteristics such as a nearly continuous spectrum and high color rendering properties. In the thesis, we combine the light-emitting diodes and quantum dot fluorescent materials to demonstrate a high optical quality, wide color gamut, and high color saturation backlight display. First, we provide a package method to keep quantum dot phosphors maintaining in highly optimal luminous efficiency. After 1000 hours reliability testing, the results show that the luminous efficiency is with about 73% decay of the traditional quantum dot package while the use of high transmittance quartz cell protection packages with the liquid quantum dots inside whose luminous efficiency is only about 13% decay. Finally, we successfully find a way to protect white quantum dot package faraway from heat and oxidation, which can maintain quantum dots performance with high luminous efficiency. The result can be implied in the backlight display in order to improve the luminous efficiency and color vivid. Second, the conventional liquid crystal displays have much energy loss, which is due to the light absorption from backlight module and color filter, and slower reaction rate than LEDs. Therefore, we utilize aerosol jet printing system to jet red, green and blue quantum dots onto the micro light-emitting diode array that can be manipulated independently. In this research, it means that we are able to produce micron light display that can light directly. It not only shortens the reaction time but also increases the utilization of light. This study provides the display which is with the much thinner thickness because it is without the liquid crystal structure to control the brightness of the screen. Moreover, the white light micron display that is manufactured by red, green, blue quantum dots can improve the color gamut of the display. The color gamut NTSC reached the ultrahigh value about 152%. Thus, we demonstrate a high vivid, saturated colors quantum dot micro display for lighting technologies, chip-scale integrated circuit and outdoor applications.