Efficient Electron Injection Mechanism in Organic Light-Emitting Diodes Using an Ultra Thin Layer of Low-Work-Function Metals

Takahito Oyamada, Chiharu Maeda, Hiroyuki Sasabe, Chihaya Adachi

Research output: Contribution to journalArticle

56 Citations (Scopus)

Abstract

To achieve efficient electron injection in organic light-emitting diodes, we examine ultra thin layers (0.50 nm) of the low-work-function metals, Cs (1.9eV), Rb (2.2eV), K (2.3eV), Na (2.4eV), Li (2.9eV), and Ca (2.9eV) capped with aluminum (Al) as a cathode layer. While all the alkali metals show a decrease of driving voltage compared with a single Al cathode, the Cs layer especially shows a significant decrease, and we obtain a high current density of 1.9 A/cm2 at an applied voltage of only 10V by using this layer. We demonstrate that efficient electron injection is achieved when we use a Cs layer with a thickness of less than 3 nm, although electron injection efficiency abruptly decreases when using a Cs layer thicker than 3 nm. From the Cs thickness dependence of current-voltage characteristics, we conclude that Cs atoms form an alloy layer with aluminum atoms at the organic/Al cathode interface, organic layer/Cs:Al/Al, that significantly enhances electron injection compared with that obtained from bulk Cs layers.

Original languageEnglish
Pages (from-to)L1535-L1538
JournalJapanese Journal of Applied Physics, Part 2: Letters
Volume42
Issue number12 B
Publication statusPublished - Dec 15 2003
Externally publishedYes

Fingerprint

Electron injection
Organic light emitting diodes (OLED)
light emitting diodes
injection
Aluminum
Metals
metals
aluminum
Cathodes
electrons
cathodes
Atoms
Electric potential
electric potential
Alkali metals
Current voltage characteristics
Current density
alkali metals
atoms
high current

All Science Journal Classification (ASJC) codes

  • Engineering(all)
  • Physics and Astronomy (miscellaneous)
  • Physics and Astronomy(all)

Cite this

Efficient Electron Injection Mechanism in Organic Light-Emitting Diodes Using an Ultra Thin Layer of Low-Work-Function Metals. / Oyamada, Takahito; Maeda, Chiharu; Sasabe, Hiroyuki; Adachi, Chihaya.

In: Japanese Journal of Applied Physics, Part 2: Letters, Vol. 42, No. 12 B, 15.12.2003, p. L1535-L1538.

Research output: Contribution to journalArticle

@article{63f9df508dfe4867a071a9447a616120,
title = "Efficient Electron Injection Mechanism in Organic Light-Emitting Diodes Using an Ultra Thin Layer of Low-Work-Function Metals",
abstract = "To achieve efficient electron injection in organic light-emitting diodes, we examine ultra thin layers (0.50 nm) of the low-work-function metals, Cs (1.9eV), Rb (2.2eV), K (2.3eV), Na (2.4eV), Li (2.9eV), and Ca (2.9eV) capped with aluminum (Al) as a cathode layer. While all the alkali metals show a decrease of driving voltage compared with a single Al cathode, the Cs layer especially shows a significant decrease, and we obtain a high current density of 1.9 A/cm2 at an applied voltage of only 10V by using this layer. We demonstrate that efficient electron injection is achieved when we use a Cs layer with a thickness of less than 3 nm, although electron injection efficiency abruptly decreases when using a Cs layer thicker than 3 nm. From the Cs thickness dependence of current-voltage characteristics, we conclude that Cs atoms form an alloy layer with aluminum atoms at the organic/Al cathode interface, organic layer/Cs:Al/Al, that significantly enhances electron injection compared with that obtained from bulk Cs layers.",
author = "Takahito Oyamada and Chiharu Maeda and Hiroyuki Sasabe and Chihaya Adachi",
year = "2003",
month = "12",
day = "15",
language = "English",
volume = "42",
pages = "L1535--L1538",
journal = "Japanese Journal of Applied Physics, Part 2: Letters",
issn = "0021-4922",
number = "12 B",

}

TY - JOUR

T1 - Efficient Electron Injection Mechanism in Organic Light-Emitting Diodes Using an Ultra Thin Layer of Low-Work-Function Metals

AU - Oyamada, Takahito

AU - Maeda, Chiharu

AU - Sasabe, Hiroyuki

AU - Adachi, Chihaya

PY - 2003/12/15

Y1 - 2003/12/15

N2 - To achieve efficient electron injection in organic light-emitting diodes, we examine ultra thin layers (0.50 nm) of the low-work-function metals, Cs (1.9eV), Rb (2.2eV), K (2.3eV), Na (2.4eV), Li (2.9eV), and Ca (2.9eV) capped with aluminum (Al) as a cathode layer. While all the alkali metals show a decrease of driving voltage compared with a single Al cathode, the Cs layer especially shows a significant decrease, and we obtain a high current density of 1.9 A/cm2 at an applied voltage of only 10V by using this layer. We demonstrate that efficient electron injection is achieved when we use a Cs layer with a thickness of less than 3 nm, although electron injection efficiency abruptly decreases when using a Cs layer thicker than 3 nm. From the Cs thickness dependence of current-voltage characteristics, we conclude that Cs atoms form an alloy layer with aluminum atoms at the organic/Al cathode interface, organic layer/Cs:Al/Al, that significantly enhances electron injection compared with that obtained from bulk Cs layers.

AB - To achieve efficient electron injection in organic light-emitting diodes, we examine ultra thin layers (0.50 nm) of the low-work-function metals, Cs (1.9eV), Rb (2.2eV), K (2.3eV), Na (2.4eV), Li (2.9eV), and Ca (2.9eV) capped with aluminum (Al) as a cathode layer. While all the alkali metals show a decrease of driving voltage compared with a single Al cathode, the Cs layer especially shows a significant decrease, and we obtain a high current density of 1.9 A/cm2 at an applied voltage of only 10V by using this layer. We demonstrate that efficient electron injection is achieved when we use a Cs layer with a thickness of less than 3 nm, although electron injection efficiency abruptly decreases when using a Cs layer thicker than 3 nm. From the Cs thickness dependence of current-voltage characteristics, we conclude that Cs atoms form an alloy layer with aluminum atoms at the organic/Al cathode interface, organic layer/Cs:Al/Al, that significantly enhances electron injection compared with that obtained from bulk Cs layers.

UR - http://www.scopus.com/inward/record.url?scp=1242265388&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=1242265388&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:1242265388

VL - 42

SP - L1535-L1538

JO - Japanese Journal of Applied Physics, Part 2: Letters

JF - Japanese Journal of Applied Physics, Part 2: Letters

SN - 0021-4922

IS - 12 B

ER -