Special Section on Organic Light-Emitting Materials and Devices

Device properties of Alq3-based organic light-emitting diodes studied by displacement current measurement

[+] Author Affiliations
Yutaka Noguchi

Chiba University, Center for Frontier Science, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan

Chiba University, Graduate School of Advanced Integration Science, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan

PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan

Takamitsu Tamura

Chiba University, Graduate School of Advanced Integration Science, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan

Hyung Jun Kim

Chiba University, Graduate School of Advanced Integration Science, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan

Hisao Ishii

Chiba University, Center for Frontier Science, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan

Chiba University, Graduate School of Advanced Integration Science, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan

J. Photon. Energy. 2(1), 021214 (Jul 18, 2012). doi:10.1117/1.JPE.2.021214
History: Received March 28, 2012; Revised May 16, 2012; Accepted June 25, 2012
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Abstract.  Displacement current measurement (DCM) is a simple but powerful tool for exploring charge carrier dynamics in organic semiconductor devices. In the first section, we review the basic concept of DCM and how it detects the charge injection, extraction, accumulation, and trapping behaviors in organic semiconductor devices within a quasistatic regime. Subsequently, we present applications of this technique to investigate the device properties of tris-(8-hydroxyquinolate) aluminum (Alq3)-based organic light-emitting diodes. We observed that light irradiation during device fabrication induces additional negative space charges and charge traps in the Alq3 layer. In addition, the device containing the illuminated Alq3 film exhibits a lower luminous efficiency and shorter lifetime compared to the device fabricated in dark conditions, possibly because of the additional hole accumulation in the illuminated Alq3 film. DCM detects the formation of charge traps in the aged devices, decay of the negative space charge, and increase in hole injection voltage with device aging. The origins of these behaviors can be attributed to orientation polarization and charge traps in Alq3 film.

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© 2012 Society of Photo-Optical Instrumentation Engineers

Citation

Yutaka Noguchi ; Takamitsu Tamura ; Hyung Jun Kim and Hisao Ishii
"Device properties of Alq3-based organic light-emitting diodes studied by displacement current measurement", J. Photon. Energy. 2(1), 021214 (Jul 18, 2012). ; http://dx.doi.org/10.1117/1.JPE.2.021214


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