Strong interfacial dipole formation with thermal evaporation of lithium cobalt oxide for efficient electron injections

Hyunbok Lee; Soohyung Park; Jeihyun Lee; Younjoo Lee; Dongguen Shin; Kwangho Jeong; Yeonjin Yi

doi:10.1063/1.4789394

Strong interfacial dipole formation with thermal evaporation of lithium cobalt oxide for efficient electron injections

Hyunbok Lee, Soohyung Park, Jeihyun Lee, Younjoo Lee, Dongguen Shin, Kwangho Jeong, Yeonjin Yi

Department of Physics

Research output: Contribution to journal › Article › peer-review

5 Citations (Scopus)

Abstract

We investigated the electronic structures at the interface of Al/lithium cobalt oxide (LiCoO₂)/tris(8-hydoxyquinoline) aluminum (Alq ₃) to elucidate the origin of the electron injection enhancement with the insertion of the LiCoO₂ layer in organic light-emitting devices using in situ photoelectron spectroscopy experiments. We discovered that LiCoO₂ was decomposed into lithium oxide (Li₂O) by thermal evaporation, and only Li₂O was deposited on the desired substrate. Li₂O forms a strong interfacial dipole, which reduces the surface potential on Alq₃ due to its extremely low work function. As a result, the electron injection barrier was dramatically decreased by the Li ₂O layer. Furthermore, there is no strong chemical interaction at the interface of Al/Li₂O/Alq₃; hence, this would contribute to extend the device lifetime.

Original language	English
Article number	033302
Journal	Applied Physics Letters
Volume	102
Issue number	3
DOIs	https://doi.org/10.1063/1.4789394
Publication status	Published - 2013 Jan 21

Bibliographical note

Funding Information:
This work was supported by the Yonsei University Research Fund of 2012 and Samsung Display Company, a research project of the National Research Foundation of Korea (Grant No. 2012-0002303).

All Science Journal Classification (ASJC) codes

Physics and Astronomy (miscellaneous)

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title = "Strong interfacial dipole formation with thermal evaporation of lithium cobalt oxide for efficient electron injections",

abstract = "We investigated the electronic structures at the interface of Al/lithium cobalt oxide (LiCoO2)/tris(8-hydoxyquinoline) aluminum (Alq 3) to elucidate the origin of the electron injection enhancement with the insertion of the LiCoO2 layer in organic light-emitting devices using in situ photoelectron spectroscopy experiments. We discovered that LiCoO2 was decomposed into lithium oxide (Li2O) by thermal evaporation, and only Li2O was deposited on the desired substrate. Li2O forms a strong interfacial dipole, which reduces the surface potential on Alq3 due to its extremely low work function. As a result, the electron injection barrier was dramatically decreased by the Li 2O layer. Furthermore, there is no strong chemical interaction at the interface of Al/Li2O/Alq3; hence, this would contribute to extend the device lifetime.",

author = "Hyunbok Lee and Soohyung Park and Jeihyun Lee and Younjoo Lee and Dongguen Shin and Kwangho Jeong and Yeonjin Yi",

note = "Funding Information: This work was supported by the Yonsei University Research Fund of 2012 and Samsung Display Company, a research project of the National Research Foundation of Korea (Grant No. 2012-0002303).",

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doi = "10.1063/1.4789394",

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AU - Lee, Hyunbok

AU - Park, Soohyung

AU - Lee, Jeihyun

AU - Lee, Younjoo

AU - Shin, Dongguen

AU - Jeong, Kwangho

AU - Yi, Yeonjin

N1 - Funding Information: This work was supported by the Yonsei University Research Fund of 2012 and Samsung Display Company, a research project of the National Research Foundation of Korea (Grant No. 2012-0002303).

PY - 2013/1/21

Y1 - 2013/1/21

N2 - We investigated the electronic structures at the interface of Al/lithium cobalt oxide (LiCoO2)/tris(8-hydoxyquinoline) aluminum (Alq 3) to elucidate the origin of the electron injection enhancement with the insertion of the LiCoO2 layer in organic light-emitting devices using in situ photoelectron spectroscopy experiments. We discovered that LiCoO2 was decomposed into lithium oxide (Li2O) by thermal evaporation, and only Li2O was deposited on the desired substrate. Li2O forms a strong interfacial dipole, which reduces the surface potential on Alq3 due to its extremely low work function. As a result, the electron injection barrier was dramatically decreased by the Li 2O layer. Furthermore, there is no strong chemical interaction at the interface of Al/Li2O/Alq3; hence, this would contribute to extend the device lifetime.

AB - We investigated the electronic structures at the interface of Al/lithium cobalt oxide (LiCoO2)/tris(8-hydoxyquinoline) aluminum (Alq 3) to elucidate the origin of the electron injection enhancement with the insertion of the LiCoO2 layer in organic light-emitting devices using in situ photoelectron spectroscopy experiments. We discovered that LiCoO2 was decomposed into lithium oxide (Li2O) by thermal evaporation, and only Li2O was deposited on the desired substrate. Li2O forms a strong interfacial dipole, which reduces the surface potential on Alq3 due to its extremely low work function. As a result, the electron injection barrier was dramatically decreased by the Li 2O layer. Furthermore, there is no strong chemical interaction at the interface of Al/Li2O/Alq3; hence, this would contribute to extend the device lifetime.

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Strong interfacial dipole formation with thermal evaporation of lithium cobalt oxide for efficient electron injections

Abstract

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