國 立 交 通 大 學
應用化學研究所
博士論文
高效率上發光有機發光元件的開發
Development of Highly Efficient Top-Emitting Light-Emitting Devices
研 究 生:徐士峯
指導教授:陳金鑫 教授
高效率上發光有機發光元件開發
Development of Highly Efficient Top-Emitting Light-Emitting Devices
研 究 生:徐士峯 Student:Shih-Feng Hsu
指導教授:陳金鑫 Advisor:Chin H. Chen
國 立 交 通 大 學
應 用 化 學 系
博 士 論 文
A ThesisSubmitted to Department of Applied Chemistry College of Science
National Chiao Tung University in partial Fulfillment of the Requirements
for the Degree of Doctor of Philosophy
Sep. 2006
Hsinchu, Taiwan
Development of Highly Efficient Top-Emitting Light-Emitting Devices
Student:Shih-Feng Hsu
Advisors:Dr.
Chin H. Chen
Department of Applied Chemistry
National Chiao Tung University
ABSTRACT
We have developed highly efficient red, green and blue top-emitting organic light-emitting devices by using Ag as the anode and cathode. We optimized microcavity effect in the devices by tuning suitable optical length for RGB emissions. A very saturated RGB color with Commission Internationale d’Eclairage (CIE) coordinates of (0.646, 0.353), (0.227, 0.721) and (0.135, 0.056) for RGB respectively were demonstrated and shown to display a color gamut of NTSC 102%. We also introduced a new hole-injection layer to get better carrier balance in the TOLEDs with which one of the best electroluminescence (EL) efficiencies for red was achieved at 37.5 cd/A .
We have also developed highly efficient white top-emitting organic light-emitting devices with broad emission by modifying both the anode and cathode. To alleviate the undesirable microcavity effect and obtain “broad” white emission, a CFx-coated Ag anode and an index-matching layer
(SnO2) capped on a thin Ca/Ag cathode with a maximum transparency of 80% were employed. A
top-emitting broad white-light device, based on the dual-layer architecture of light blue and yellow emitters with one of the highest EL efficiencies of 22.2 cd/A (9.6 lm/W) at 20 mA/cm2and 7.3 V with CIE coordinates of (x=0.31, y=0.47), has been demonstrated.
Contents
Chapter 1
Introduction
1
1.1 Overview of OLED devices and displays……….……… 1
1.2 Motivation……….………… 3
1.3 Thesis outlines……….. 5
Chapter 2
Color-saturated top-emitting organic light-emitting devices
7
2.1 Introduction……….. 72.2 Experimental …….……….……… 9
2.3 Results and discussions……… 11
2.3.1 Alq-based devices with various thickness of ITO……… 11
2.3.2 Optimized TOLEDs with RGB emissive colors……… 13
2.3.3 Viewing angle of Alq-based and RGB TOLEDs ……… 17
Chapter 3
Highly efficient top-emitting organic light-emitting devices
21
3.1 Optical simulation……… 21 3.2 3.2.1 .3.2.2 .3.2.3 3.3 3.4 High efficiency TOLED devices……….… Ca/Ag system……….. N-doping ETL/Ag system……… New HIMs system………. Power consumption simulation of TOLEDs…….... WTOLEDs on TFT array……….. 23 24 25 28 32 37Chapter 4
White light top-emitting organic light-emitting devices
38
4.1 Introduction………... 38 4.2 4.2.1 4.2.2 4.2.3 4.2.4White light top-emitting organic light-emitting devices with a dual-cavity structure………
Single-cavity WTOLEDs……… Simulation and experimental comparisons of single-cavity WTOLEDs…… Using Al/ITO as the separating layer in a dual-cavity structure……… Using Ni as the separating layer in a dual-cavity structure………
41 42 46 48 51
.4.3
4.4 4.4.1 4.4.2
White light top-emitting organic light-emitting devices with a highly transparent cathode………...… Highly efficient top-emitting white organic electroluminescent devices….
Device characteristics of WTOLEDs………
WTOLEDs on TFT array……….
56 63 64 69
Chapter 5
High-efficiency and easily manufactured top-emitting white
organic electroluminescent devices
73
5.1 WTOLEDs with a single blue dopant……….……… 73 5.2 WTOLEDs with a stacked structure……….……… 81
Chapter 6
Summary and future prospects
85
6.1 Summary………..………. 85 6.2 Future prospects……… 86