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Please use this identifier to cite or link to this item: http://hdl.handle.net/10119/10868

Title: Enhancement of hole injection and electroluminescence characteristics by a rubbing-induced lying orientation of alpha-sexithiophene
Authors: Matsushima, Toshinori
Murata, Hideyuki
Keywords: Organic light emitting diode
rubbing
molecular orientation
ionization energy
hole-pnly device
Issue Date: 2012-07-17
Publisher: American Institute of Physics
Magazine name: Journal of Applied Physics
Volume: 112
Number: 2
Start page: 024503-1
End page: 024503-9
DOI: 10.1063/1.4735402
Abstract: The authors find that rubbing a film of alpha-sexithiophene (α-6T) with a nylon cloth induces a change from standing to lying orientations in a film surface region. While current densities of hole-only devices based on 4,4′,4″-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine (m-MTDATA) are independent of the rubbing number of α-6T, current densities of hole-only devices based on N-N′-diphenyl-N-N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) and 4,4′-bis(carbazol-9-yl)-2,2′-biphenyl (CBP) markedly increase (≈42 times at 1 V for the α-NPD devices and ≈236 times at 1 V for the CBP devices) as the rubbing number of α-6T is increased. The increase in current density is ascribed to enhanced hole injection through a −5.28 eV energy level of lying α-6T domains instead of a −4.95 eV energy level of standing α-6T domains and improved overlaps between an electronic cloud of indium tin oxide, π orbitals of lying α-6T molecules, and π orbitals of molecules of α-NPD and CBP at heterojunction interfaces. The rubbing of α-6T is also demonstrated to reduce drive voltages (by ≈40% at 10 mA/cm^2) and increase power conversion efficiency (by ≈26% at 10 mA/cm^2) of organic light-emitting diodes. Finally, half lifetimes are significantly enhanced (4.3 times) at a current density of 50 mA/cm^2.
Rights: Copyright 2012 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Toshinori Matsushima and Hideyuki Murata, Journal of Applied Physics, 112(2), 024503 (2012) and may be found at http://dx.doi.org/10.1063/1.4735402
URI: http://hdl.handle.net/10119/10868
Material Type: publisher
Appears in Collections:c10-1. 雑誌掲載論文 (Journal Articles)

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