利用布拉格反射鏡製作之高發光效率與高光品質之前瞻量子點發光照明元件

Abstract

本論文中，我們提出利用新穎的膠狀量子點發光材料製作出高品質發光照明元件，並利用布拉格反射鏡共振的原理增加元件之發光效率。論文將分為兩部份，分別討論色彩飽和度大幅提升的量子點顯示器背光模組及擁有卓越光品質之量子點發光二極體。 第一部分將會對單色光與白光量子點發光二極體做研究，由於量子點擁有量子尺寸效應及極窄的發光半高寬，因此可發展擁有不同發光波長之高色純度單色發光二極體。此外透過布拉格反射鏡反射未被量子點吸收的紫外光，我們可以大幅提升量子點對紫外光的利用率，進而增加發光二極體的發光效率。另一方面藉由布拉格反射鏡反射率與入射角的相互關係，我們可以大幅改善量子點白光發光二極體的色溫均勻度，使暖白光源的變角度色溫差控制在40 K，再結合紅、綠、藍量子點三色混光所擁有的高演色性特性，我們成功製作出發光效率大幅提升的高光品質量子點白光發光二極體。 再者，我們結合脈衝噴塗技術與布拉格反射鏡製作出高品質、高效率的顯示器發光元件，利用脈衝噴塗我們可以均勻的噴塗一層大範圍薄型量子點發光層，並利用PDMS透明層來間隔不同顏色量子點，避免不同顏色量子點互相汙染。此外我們也在底層加入布拉格反射鏡，透過上述增加量子點對於紫外光利用率的原理，可大幅提升發光元件之發光強度。此外利用紅、綠、藍量子點所製作的白光背光元件可以大幅的提升顯示器的色域範圍，使色域達到NTSC 135 %的優異色彩表現，如此顯示器可提供更鮮豔、飽和的色彩，相信將會成為未來顯示器的選擇。

In this thesis, we proposed the novel quantum dot (QD) light-emitting devices with luminous enhancement by resonance of Distributed Bragg Reflector (DBR). Both the full color QD thin film displays with improved color saturation and QD white light-emitting diodes (LEDs) with significantly high light quality were discussed respectively. First, the quantum dot light-emitting diodes were studied for both monochromatic and white light QD-LEDs. Since the size-tunable characteristic and ultra-thin bandwidth of QD, we can develop a saturated monochromatic QD-LED with customized wavelengths. Besides, by the tri-chromatic mixing, the CRI of the white-LED could reach to the value over 90 since red, blue, green QDs covered the whole visible spectrum. Besides, the DBR structure with stop-band at UV region was proposed to significantly enhance the luminous output of white-LED by reflecting the unconverted UV light back to the package to further excite the QDs. Furthermore, the angular CCT uniformity of QDs white-LED could also be tremendously improved by the DBR because the dependent relationship between reflectivity of DBR and incident angle of UV light. The CCT deviation could even reduce to 40 K for warm-white source. In short, we proposed a high light quality QDs white-LED with intensity enhancement by DBR structure which is regarded as a competitive lighting source in high color quality demanded lighting application. Second, the QD thin-film display was researched for both white light surface backlight source and RGB pixelated array thin film display. High quality and high efficiency QD light-emitting devices were fabricated by using the pulse-spray coating method, which can yield a large area, uniform and thin light emitting layer. The RGB pixelated arrays light emitting device, full color white light surface source, and QD white-LED were demonstrated and discussed respectively in our research. Owing to the resonance of DBR structure, the emissions intensity of light emitting devices can be considerable enhanced because of improvement of utilization efficiency of QDs as mention above. Besides, the polydimethylsiloxane (PDMS) film was used as the interface layer between each RGB color to avoid cross-contamination and self-assembly of QDs. Furthermore, the color gamut of the proposed QD-white light-emitting device can reach to 135 % according NTSC standard, which is favorable characteristic for the next generation high-quality display technology.