Ingenium 2021
Simulating the effect of different structures and materials on OLED extraction efficiency Benjamin Bailey, Paul Leu Department of Industrial Engineering Ben Bailey was born and raised in Mount Pleasant, Pennsylvania. His research interests are nanostructures and using them to increase efficiency in OLEDs.
Ben Bailey
Dr. Leu is an Associate Professor in the Department of Industrial Engineering and the Department of Mechanical Engineering and Materials Science. He received his BS in Mechanical Engineering at Rice University in 2002, his MS from Stanford University in 2004, and his PhD from Stanford University Paul Leu, Ph.D. in 2008. Dr. Leu’s lab research focuses on designing and understanding advanced materials by computational modeling and experimental research.
Significance Statement
Organic light-emitting diodes (OLEDs) have lower efficiency than other types of lights. With a lower efficiency, more power is required to use OLEDs. Using microstructures on the surface of the OLED increases efficiency by decreasing the reflectivity of the light generated within the structure.
Category: Computational Research
Keywords: OLED, EE, Nanocone, FDTD
Abstract
In order to increase the extraction efficiency (EE), the transmission of light generated in the structure must be maximized. With a maximized EE, there is less power required to produce the same amount of light. This goal is achieved by using surface structures on top of the glass layer of an organic light-emitting diode (OLED) device. Among all the available structures, we focus on the nanocones in this research, because the nanocone structures in previous studies displayed more extraction enhancement than other simple structures. Also, this research is a basis to begin a larger project, with more complicated structures, that time limitations prevented us from going deeper into. Using finite-difference time-domain (FDTD) analysis, the size of the nanocones can be optimized to maximize EE. It was found that minimizing the surface area not covered by nanocones, as the distance between nanocones was the largest factor in the simulations.
1. Introduction
Organic light-emitting diodes (OLEDs) are devices that emit light when electricity is transferred from a cathode, through an organic emissive layer, to an anode. Light is emitted from the emissive layer and extracted from the device. The efficiency of the OLED describes how much power is output by light compared to the electrical input. High efficiency OLEDs are desirable as less electricity, or energy, required to light anything from a smart card with an OLED display to lighting devices for homes and businesses. The purpose behind this project is to maximize the efficiency of OLED devices by optimizing nanocone structures in a square lattice symmetry. Lim et al. studied the efficiency of different nanostructures on the surface of OLEDs; they found that the external quantum efficiency (EQE) of nanocones in a square lattice symmetry is fourteen to thirty-five percent [1]. Kim et al. corroborated the results of the nanocone structures, reaching 31.8 percent extraction efficiency (EE) [2]. This study will begin the study of EE using various nanostructures to continue increasing the efficiency of OLEDs. Since light is reflected back into the device when entering a flat layer, it could be hypothesized that the angle of the sides of the nanocones will be the most important factor. This angle is from changing the top radius, the bottom radius, and the height of the cone. The larger the difference between the two radii along with a low height would give a smaller angle, while decreasing the difference between the two radii and increasing the height would increase the angle. This study differs from other studies by comparing the different sizes of nanocones used to increase EE. Also, the majority of past research on this topic was done in a lab, while the work shown in this paper is simulated using FDTD analysis.
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