Electronic structure of organic carrier transporting material / metal interfaces as a model interface of electroluminescent device studied by UV photoemission

Sugiyama, K.; Yoshimura, Daisuke; Ito, Eisuke; Miyazaki, Tsuyoshi; Hamatani, Y.; Kawamoto, Ippei; Ishii, Hisao; Ouchi, Yukio; Seki, Kazuhiko

doi:10.1016/s0379-6779(97)81185-x

Cited by 24 publications

(8 citation statements)

References 4 publications

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“…A positive barrier is blocking, and a negative or zero barrier passes carriers. It has been well documented that the assumption of vacuum level alignment at metal/organic interfaces is not valid, [5][6][7][8][9][10][11] thus prompting careful examination of the electronic structure of a number of organic semiconductor heterojunctions. Using UPS, we have measured the barriers to hole injection, and the magnitude of the interface dipole ͑vacuum level shift͒, at two organic/organic interfaces: CBP/Alq 3 and ␣-NPD/CuPc.…”

Section: Introductionmentioning

confidence: 99%

Energy level alignment at interfaces of organic semiconductor heterostructures

Hill

Kahn

1998

Journal of Applied Physics

154

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We have used ultraviolet photoelectron spectroscopy ͑UPS͒ to investigate the interfaces of two organic semiconductor heterostructures. UPS was used to determine the relative energies of the highest occupied molecular orbitals of the organic semiconductors, and to measure the interface dipoles at each interface. The two systems studied were the 4-4Ј-N,NЈ-dicarbazolyl-biphenyl͑CBP͒/tris͑8-hydroxy-quinoline͒aluminum (Alq 3) interface, and the copper phthalocyanine (CuPc)/N,NЈ-diphenyl-N,NЈ-bis͑1-naphthyl͒-1,1Јbiphenyl-4,4Љdiamine ͑␣-NPD͒ interface. The assumption of a common vacuum level was found to be valid, within experimental uncertainty, for both interfaces.

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Section: Introductionmentioning

confidence: 99%

Energy level alignment at interfaces of organic semiconductor heterostructures

Hill

Kahn

1998

Journal of Applied Physics

154

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“…Technology has so far relied on empirical solutions to these problems and there is considerable incentive at this point to further our understanding of the electronic structure and chemical properties of metalorganic interfaces. [1][2][3][4][5][6][7][8][9][10][11][12] The subject of this letter is one which has long been debated for metal/inorganic semiconductor junctions, namely, the degree to which the barriers vary with the metal work function ( M ). At metal/organic semiconductor interfaces, the hole and electron barriers ( Bh and Be in Fig.…”

mentioning

confidence: 99%

Molecular level alignment at organic semiconductor-metal interfaces

Hill

Rajagopal

Kahn

et al. 1998

Applied Physics Letters

447

283

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In order to clarify the electronic structure of metal-molecular semiconductor contacts, we use photoemission spectroscopy to investigate the energetics of interfaces formed by vacuum deposition of four different molecular thin films on various metals. We find that the interface electron and hole barriers are not simply defined by the difference between the work functions of the metals and organic solids. The range of interface Fermi level positions is material dependent and dipole barriers are present at all these interfaces. The results demonstrate the breakdown of the vacuum level alignment rule at interfaces between these organic molecular solids and metals.

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“…[12][13][14][15][16][17][18] However, up to this point, the interfaces with mixed layers of metal and organic materials have not been studied. [12][13][14][15][16][17][18] However, up to this point, the interfaces with mixed layers of metal and organic materials have not been studied.…”

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confidence: 99%

Photoemission spectroscopy study of Alq3 and metal mixed interfaces

Kwon¹,

Kim²,

Kim³

et al. 2001

Applied Physics Letters

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Role of metal-molecule chemistry and interdiffusion on the electrical properties of an organic interface: The Al-F 16 CuPc case Determination of the orbital lineup at reactive organic semiconductor interfaces using photoemission spectroscopyThe electronic structures of mixed layers of tris ͑8-hydroxy-quinoline͒ aluminum ͑Alq3͒ and metal ͑Au and Al͒ were studied by ultraviolet and x-ray photoelectron spectroscopy ͑UPS and XPS͒. The devices with a mixed layer between Alq3 and the cathode were fabricated. The barrier height for electron injection was reduced by doping metals ͑Au or Al͒ into Alq3. The doping enhanced the performance of the device. From the XPS study, the doped Au metal did not react with Alq3 and in addition, the doped Al metal reacted slightly with Alq3. From the UPS study, the highest occupied molecular orbit shifted to a higher binding energy for both metal mixed layers. From these studies, it is concluded that the enhanced device characteristics come from the barrier height reduction by the metal doped in Alq3 rather than from the charge transfer complex induced by the reaction of Alq3 and metal.

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Electronic structure of organic carrier transporting material / metal interfaces as a model interface of electroluminescent device studied by UV photoemission

Cited by 24 publications

References 4 publications

Energy level alignment at interfaces of organic semiconductor heterostructures

Energy level alignment at interfaces of organic semiconductor heterostructures

Molecular level alignment at organic semiconductor-metal interfaces

Photoemission spectroscopy study of Alq3 and metal mixed interfaces

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