ITO is being used widely as a transparent conducting electrode for OLED. Surface roughness and microstructure of ITO have been known to give important influence on the OLED performance. However the effect of the both couldn’t be separated with ITO made by same method. In this study, 4 ITOs deposited using a conventional capacitive RF magnetron sputtering, a new facing target DC sputtering and two post-annealed of these samples were compared.

The grain structure, surface roughness, electrical and optical property of the ITO were investigated by XRD, FESEM, AFM, 4 point probe and UV spectrophotometer, and those are related to the resultant I-V-L characteristic of OLED.The grain structure of ITO by capacitive RF magnetron sputtering was almost columnar, on the while that by facing target DC sputtering was equi axed at the as deposited condition. By the post annealing, the grain structure by capacitive RF magnetron sputtering changed to the totally columnar but that by facing target DC sputtering maintained an equi axed only just with some grain growth. The RMS surface roughness of the ITO was 0.9nm and 0.2nm, respectively at the as deposited condition. After the post-annealing, that was increased by 5.4nm and 1.5nm. Both ITO films showed amorphous structure at the as deposited condition were crystallized with a same (400) preferred growth orientation and the transparency was improved by post annealing.

From the I-V-L characteristic, we could see that the threshold voltage and luminescence of the OLED was better with ITO of annealed facing target DC sputtering that sustains a compact and fine equi axed grains with appropriate surface roughness. This result means that there is a lower limit of RMS surface roughness about 1 to 1.5nm to give an effective carrier injection and above the limit the compact equi axed grain structure become more effective for good OLED. With ITO of annealed facing target DC sputtering, OLED with V_th of less than 6 volts was obtained.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/15673 must be provided.