Optical Design of Organic Light-Emitting Devices Based on Microcavity Effect
Date Issued
2012
Date
2012
Author(s)
Wong, Jhih-Kai
Abstract
There are many advantages on the organic light-emitting device (OLED), such as, self-emission, slimmer shape, flexibility, larger color gamut, low power consumption, wide viewing angle, faster response time and lower cost. The OLED will play an important role among the next generation of mainstream displays. However, the physical scale of the OLED is about one or two hundred nanometers. The stack of organic films causes the optical interference effect in the visible region. So we introduce the microcavity effect to analyze the structure of OLEDs. About the microcavity effect, the two main mechanisms are wide-angle and multi-beam interference. And we discuss both mechanisms which influence the emission spectrum and intensity distribution of the OLEDs.
In this thesis, we demonstrate an optical model to simulate the emission spectrum, intensity distribution and other optical characteristics of the OLEDs by varying their thin-film structure and viewing angle. Next, we combine the microcavity theory to design and optimize the OLEDs. In a design process, we first consider the wide-angle interference to design the emission zone to optimize the OLEDs. Then we use the multi-beam interference to calculate the total optical thickness in the microcavity in order to design optimized device. Furthermore, we discuss the design which combines the bottom-emitting OLEDs and distributed Bragg reflector. It can improve 64% intensity and narrow the full-width half maximum of the emission spectrum from 52 nm to 33 nm. As well, we design the capping layer on the cathode of the top-emission OLEDs and discuss the influence on it. We find that the variation of the phase shift and reflectivity of the cathode will change the emission spectrum and the intensity. Therefore, we modulate the thickness of the electric transport layer to maintain the resonant wavelength of the cavity. When the reflectivity of the anode is higher 36~39% than that of the cathode, the optimum emission at the normal direction can be obtained. Eventually, we use this structure to design the common structure for red, green and blue emission. For the purpose, we modulate the thickness of the electric transport layer to achieve a RGB OLEDs of high intensity and wide color gamut.
Subjects
OLED
microcavity
optical simulation
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-101-R99941091-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):e5be9c47211d06bb8f18a01e3be0a620