High resolution Liquid-Crystal-Display using Environmentally-Friendly Quantum Dots Functional Color-filters

Abstract

Liquid-crystal-displays have the advantages of high efficiency, long lifetime, price competitiveness and simple optical configuration. In the last half century, research in industries and academy have led TFT-LCD to an unparalleled position in display technology. However, as the demand for real-world displays increases, BT. 2020, the color gamut standard for UHD TVs, has been established. The LCD has a broad spectrum of backlight units, which limits wide color gamut. To satisfy the UHD-TV standard, we used quantum dots with high PL-QY and narrow full-width at half-maximum characteristics. There is existing research to expand the color gamut of LCD using cadmium-based quantum dot. However, RoHS has restricted the use of cadmium in electronic devices. Therefore, we tried to improve color performance of LCD by using InP, a prospective material to replace cadmium based quantum dots. In addition, the quantum dot was added to the existing color filter to solve the transparency decrease of the quantum dot enhancement film method. InP itself has a very low PL-QY of 2-4% and even this easily degrades. Thus, shell passivation and defect passivation using ligands are essential. We developed suitable method for the selection of shell materials, mole concentration optimization, and synthesis method for effective core and shell growth and ligand passivation. As a result, PL-QYs of green and red emitting quantum dots are 85% and 55%. We mixed synthesized quantum dots with the color filter and measured the R-,G-,B- emission spectrum. As a result, we found that cross-talks between red and green in emission spectrum is significantly reduced than bare color filters. In the case of color gamut, the maximum over 81.4% (108.8%) of BT.2020 standard (NTSC standard) was achieved compared to bare color filter case was 55.1%. In this paper, we first describe display technology trend and quantum dots in Chapter 1 and demonstrate the displays using quantum dots, which is the core theme of this paper will be described. Chapter 2 explains the basic theory, photo luminescence mechanism of quantum dots . Chapter 3 will demonstrate the synthesis process of InP core/shell green and red emitting quantum dots and implementation of quantum dots in color filters, and Chapter 4 will cover the results of the experiment. Finally, Chapter 5 consists of conclusions.|액정 디스플레이는 고효율, 긴 수명, 가격 경쟁력 및 간단한 광학 구성의 장점을 가지고 있다. 지난 반세기 동안, 산업 및 학계는 TFT-LCD를 디스플레이 기술에서 비교할 수없는 위치로 이끌었다. 그러나 현실을 재현한 디스플레이에 대한 수요가 증가함에 따라 BT. UHD-TV의 색 영역 표준 인 2020이 확립되었다. LCD는 광범위한 방출 스펙트럼의 백라이트 유닛이 있어 넓은 색 영역을 제한한다. UHD-TV 표준을 만족시키기 위해, 우리는 높은 PL-QY와 좁은 FWHM특성을 갖는 양자점을 사용하였다. 카드뮴 기반 양자점을 사용하여 LCD의 색 영역을 확장하기 위한 기존 연구가 있다. 그러나 RoHS는 전자 장치에서 카드뮴 사용을 제한했다. 따라서 카드뮴 기반의 양자점을 대체 할 수 있는 재료 인 InP를 사용하여 LCD의 색상 성능을 개선하고자 했다. 또한, 기존의 컬러 필터에 양자점을 추가하여 양자점 향상 필름 방법의 투과도 감소를 해결 하였다. InP 자체는 2-4 %의 매우 낮은 PL-QY를 가지고 있으며 이조 차도 쉽게 저하된다. 따라서, 리간드를 이용한 쉘 패시베이션 및 결함 패시베이션이 필수적이다. 우리는 효과적인 코어 및 쉘 성장 및 리간드 패시베이션을위한 쉘 재료의 선택, 몰 농도 최적화 및 합성 방법에 적합한 방법을 개발했다. 결과적으로 녹색 및 적색 방출 양자점의 PL-QY는 85 % 및 55 %이다. 합성된 양자점을 컬러 필터와 혼합하고 R-, G-, B- 방출 스펙트럼을 측정하였다. 그 결과, 방출 스펙트럼에서 적색과 녹색 사이의 크로스토크가 베어 컬러 필터보다 현저히 줄어드는 것을 발견했다. 색 영역의 경우, BT.2020 표준 (NTSC 표준)의 최대 81.4 % (108.8 %) 이상이었고 베어 컬러 필터 케이스와 비교하여 55.1 %였다. 본 논문에서는 먼저 1 장의 디스플레이 기술 트렌드와 양자점을 설명하고 본 논문의 핵심 주제 인 양자점을 사용한 디스플레이를 설명한다. 2 장에서는 양자점의 기본 이론, 광 발광 메커니즘에 대해 설명한다. 3 장에서는 InP 코어 / 쉘 녹색 및 적색 방출 양자점의 합성 과정과 컬러 필터에서의 양자점 구현에 대해 설명하고 4 장에서는 실험 결과를 다룰 것이다. 마지막으로 5 장은 결론으로 ​​구성된다.; Liquid-crystal-displays have the advantages of high efficiency, long lifetime, price competitiveness and simple optical configuration. In the last half century, research in industries and academy have led TFT-LCD to an unparalleled position in display technology. However, as the demand for real-world displays increases, BT. 2020, the color gamut standard for UHD TVs, has been established. The LCD has a broad spectrum of backlight units, which limits wide color gamut. To satisfy the UHD-TV standard, we used quantum dots with high PL-QY and narrow full-width at half-maximum characteristics. There is existing research to expand the color gamut of LCD using cadmium-based quantum dot. However, RoHS has restricted the use of cadmium in electronic devices. Therefore, we tried to improve color performance of LCD by using InP, a prospective material to replace cadmium based quantum dots. In addition, the quantum dot was added to the existing color filter to solve the transparency decrease of the quantum dot enhancement film method. InP itself has a very low PL-QY of 2-4% and even this easily degrades. Thus, shell passivation and defect passivation using ligands are essential. We developed suitable method for the selection of shell materials, mole concentration optimization, and synthesis method for effective core and shell growth and ligand passivation. As a result, PL-QYs of green and red emitting quantum dots are 85% and 55%. We mixed synthesized quantum dots with the color filter and measured the R-,G-,B- emission spectrum. As a result, we found that cross-talks between red and green in emission spectrum is significantly reduced than bare color filters. In the case of color gamut, the maximum over 81.4% (108.8%) of BT.2020 standard (NTSC standard) was achieved compared to bare color filter case was 55.1%. In this paper, we first describe display technology trend and quantum dots in Chapter 1 and demonstrate the displays using quantum dots, which is the core theme of this paper will be described. Chapter 2 explains the basic theory, photo luminescence mechanism of quantum dots . Chapter 3 will demonstrate the synthesis process of InP core/shell green and red emitting quantum dots and implementation of quantum dots in color filters, and Chapter 4 will cover the results of the experiment. Finally, Chapter 5 consists of conclusions.