Improving Luminous Efficiency and Light Quality of Cutting-edge Quantum Dots Light-Emitting Devices using Distributed Bragg Reflector
|關鍵字:||發光二極體;量子點螢光粉;布拉格反射鏡;Light-emitting diode;Quantum dot;Distributed Bragg Reflector|
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.