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Title: Enhancement of hole injection using ozone treated Ag nanodots dispersed on indium tin oxide anode for organic light emitting diodes

Abstract

The authors report the enhancement of hole injection using an indium tin oxide (ITO) anode covered with ultraviolet (UV) ozone-treated Ag nanodots for fac tris (2-phenylpyridine) iridium Ir(ppy){sub 3}-doped phosphorescent organic light-emitting diodes (OLEDs). X-ray photoelectron spectroscopy and UV-visible spectrometer analysis exhibit that UV-ozone treatment of the Ag nanodots dispersed on the ITO anode leads to formation of Ag{sub 2}O nanodots with high work function and high transparency. Phosphorescent OLEDs fabricated on the Ag{sub 2}O nanodot-dispersed ITO anode showed a lower turn-on voltage and higher luminescence than those of OLEDs prepared with a commercial ITO anode. It was thought that, as Ag nanodots changed to Ag{sub 2}O nanodots by UV-ozone treatment, the decrease of the energy barrier height led to the enhancement of hole injection in the phosphorescent OLEDs.

Authors:
; ; ; ; ; ; ; ;  [1];  [2];  [2]
  1. School of Advanced Materials and Systems Engineering, Kumoh National Institute of Technology (KIT), Gumi 730-701 (Korea, Republic of)
  2. (Korea, Republic of)
Publication Date:
OSTI Identifier:
20960232
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 90; Journal Issue: 16; Other Information: DOI: 10.1063/1.2719153; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANODES; BEAM INJECTION; DOPED MATERIALS; ELECTRIC POTENTIAL; HOLES; INDIUM COMPOUNDS; IRIDIUM; LIGHT EMITTING DIODES; ORGANIC SEMICONDUCTORS; OZONE; PHOSPHORESCENCE; QUANTUM DOTS; SILVER OXIDES; SPECTROMETERS; TIN OXIDES; ULTRAVIOLET RADIATION; ULTRAVIOLET SPECTRA; VISIBLE SPECTRA; WORK FUNCTIONS; X-RAY PHOTOELECTRON SPECTROSCOPY

Citation Formats

Moon, Jong-Min, Bae, Jung-Hyeok, Jeong, Jin-A, Jeong, Soon-Wook, Park, No-Jin, Kim, Han-Ki, Kang, Jae-Wook, Kim, Jang-Joo, Yi, Min-Su, Department of Materials Science and Engineering, Seoul National University, Silim-dong, Seoul 151-741, Korea and Center for Organic Light Emitting Diodes, Seoul National University, Silim-dong, Seoul 151-741, and Department of Materials Science and Engineering, Sangju National University, Sangju, Gyeongbuk 742-711. Enhancement of hole injection using ozone treated Ag nanodots dispersed on indium tin oxide anode for organic light emitting diodes. United States: N. p., 2007. Web. doi:10.1063/1.2719153.
Moon, Jong-Min, Bae, Jung-Hyeok, Jeong, Jin-A, Jeong, Soon-Wook, Park, No-Jin, Kim, Han-Ki, Kang, Jae-Wook, Kim, Jang-Joo, Yi, Min-Su, Department of Materials Science and Engineering, Seoul National University, Silim-dong, Seoul 151-741, Korea and Center for Organic Light Emitting Diodes, Seoul National University, Silim-dong, Seoul 151-741, & Department of Materials Science and Engineering, Sangju National University, Sangju, Gyeongbuk 742-711. Enhancement of hole injection using ozone treated Ag nanodots dispersed on indium tin oxide anode for organic light emitting diodes. United States. doi:10.1063/1.2719153.
Moon, Jong-Min, Bae, Jung-Hyeok, Jeong, Jin-A, Jeong, Soon-Wook, Park, No-Jin, Kim, Han-Ki, Kang, Jae-Wook, Kim, Jang-Joo, Yi, Min-Su, Department of Materials Science and Engineering, Seoul National University, Silim-dong, Seoul 151-741, Korea and Center for Organic Light Emitting Diodes, Seoul National University, Silim-dong, Seoul 151-741, and Department of Materials Science and Engineering, Sangju National University, Sangju, Gyeongbuk 742-711. Mon . "Enhancement of hole injection using ozone treated Ag nanodots dispersed on indium tin oxide anode for organic light emitting diodes". United States. doi:10.1063/1.2719153.
@article{osti_20960232,
title = {Enhancement of hole injection using ozone treated Ag nanodots dispersed on indium tin oxide anode for organic light emitting diodes},
author = {Moon, Jong-Min and Bae, Jung-Hyeok and Jeong, Jin-A and Jeong, Soon-Wook and Park, No-Jin and Kim, Han-Ki and Kang, Jae-Wook and Kim, Jang-Joo and Yi, Min-Su and Department of Materials Science and Engineering, Seoul National University, Silim-dong, Seoul 151-741, Korea and Center for Organic Light Emitting Diodes, Seoul National University, Silim-dong, Seoul 151-741 and Department of Materials Science and Engineering, Sangju National University, Sangju, Gyeongbuk 742-711},
abstractNote = {The authors report the enhancement of hole injection using an indium tin oxide (ITO) anode covered with ultraviolet (UV) ozone-treated Ag nanodots for fac tris (2-phenylpyridine) iridium Ir(ppy){sub 3}-doped phosphorescent organic light-emitting diodes (OLEDs). X-ray photoelectron spectroscopy and UV-visible spectrometer analysis exhibit that UV-ozone treatment of the Ag nanodots dispersed on the ITO anode leads to formation of Ag{sub 2}O nanodots with high work function and high transparency. Phosphorescent OLEDs fabricated on the Ag{sub 2}O nanodot-dispersed ITO anode showed a lower turn-on voltage and higher luminescence than those of OLEDs prepared with a commercial ITO anode. It was thought that, as Ag nanodots changed to Ag{sub 2}O nanodots by UV-ozone treatment, the decrease of the energy barrier height led to the enhancement of hole injection in the phosphorescent OLEDs.},
doi = {10.1063/1.2719153},
journal = {Applied Physics Letters},
number = 16,
volume = 90,
place = {United States},
year = {Mon Apr 16 00:00:00 EDT 2007},
month = {Mon Apr 16 00:00:00 EDT 2007}
}
  • We report the enhancement of hole injection using AgO{sub x} layer between Ag anode and 4,4{sup '}-bis[N-(1-naphtyl)-N-phenyl-amino]biphenyl in top-emitting organic light-emitting diode (OLED). The turn-on voltage of OLEDs decreased from 17 to 7 V as Ag changed to AgO{sub x} by the surface treatment using O{sub 2} plasma. Synchrotron radiation photoelectron spectroscopy results showed that the work function increased about 0.4 eV by the O{sub 2} plasma treatment. This led to the decrease of the energy barrier for hole injection, reducing the turn-on voltage of OLEDs.
  • We report the enhancement of hole injection and electroluminescence (EL) in an organic light emitting diode (OLED) with an ordered Ag nanodot array on indium-tin-oxide (ITO) anode. Until now, most researches have focused on the improved performance of OLEDs by plasmonic effects of metal nanoparticles due to the difficulty in fabricating metal nanodot arrays. A well-ordered Ag nanodot array is fabricated on the ITO anode of OLED using the nanoporous alumina as an evaporation mask. The OLED device with Ag nanodot arrays on the ITO anode shows higher current density and EL enhancement than the one without any nano-structure. Thesemore » results suggest that the Ag nanodot array with the plasmonic effect has potential as one of attractive approaches to enhance the hole injection and EL in the application of the OLEDs.« less
  • The degradation of organic light-emitting diodes (OLEDs) is a very complex issue, which might include interfacial charge accumulation, material diffusion, and electrical-induced chemical reaction during the operation. In this study, the origins of improvement in device stability from inserting a hole injection layer (HIL) at the indium tin oxide (ITO) anode are investigated. The results from aging single-layer devices show that leakage current increases in the case of ITO/hole transport layer contact, but this phenomenon can be prevented by inserting molybdenum oxide (MoO{sub 3}) or 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN{sub 6}) as an HIL. Moreover, X-ray photoemission spectroscopy suggests that the diffusionmore » of indium atoms and active oxygen species can be impeded by introducing MoO{sub 3} or HAT-CN{sub 6} as an HIL. These results reveal that the degradation of OLEDs is related to indium and oxygen out-diffusion from the ITO substrates, and that the stability of OLEDs can be improved by impeding this diffusion with HILs.« less
  • Local surface work-function (WF) measurement on indium-tin-oxide (ITO) films prepared by different cleaning methods for use as anode materials in organic light-emitting diodes were studied using scanning surface-potential microscopy. The ITO WF changes with standard wet-cleaning treatment correspond directly to asperities on the film surface. The maximum difference value (MDV) in the local WF reached 0.41 eV. However, after wet-cleaning ITO with the ultraviolet ozone or O-plasma treatment, the WF distribution is more uniform than the original distribution. Owing to the sufficient ITO surface oxidization, the mean local WF value increases effectively to more than 5.00 eV and the MDVmore » is less than 0.05 eV. Furthermore, the changes in roughness and conductivity on the ITO surface at different treatment times are also discussed. The proper exposure time for the O-plasma treatment can thereby be determined.« less
  • The characteristics of green phosphorescent organic light-emitting diodes (OLEDs) fabricated on ITO/glass substrates pretreated with low-energy O{sub 2} and Cl{sub 2} plasma were compared. At 20 mA/cm{sup 2}, the OLEDs with O{sub 2} and Cl{sub 2} plasma-treated indium tin oxide (ITO) had voltages of 9.6 and 7.6 eV, and brightness of 9580 and 12380 cd/m{sup 2}, respectively. At {approx}10{sup 4} cd/m{sup 2}, the latter had a 30% higher external quantum efficiency and a 74% higher power efficiency. Photoelectron spectroscopies revealed that Cl{sub 2} plasma treatment created stable In-Cl bonds and raised the work function of ITO by up to 0.9more » eV. These results suggest that the better energy level alignment at the chlorinated ITO/organic interface enhances hole injection, leading to more efficient and more reliable operation of the OLEDs. The developed plasma chlorination process is very effective for surface modification of ITO and compatible with the fabrication of various organic electronics.« less