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Influence of the electrophoretic suspension on the underlayers in organic based devices

D. MLADENOVA1,2, D. DIMOV1, D. KARASHANOVA1, S. BOYADZHIEV2, T. DOBREVA3, D. BUDUROVA4, V. SINIGERSKY4, I. ZHIVKOV1

Affiliation

  1. Central Laboratory of Photoprocesses “Acad. J. Malinowski”, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. bl. 109, 1113 Sofia, Bulgaria
  2. Department of Microelectronics, Technical University of Sofia, Kl. Ochridski Blvd. 8, 1756 Sofia, Bulgaria
  3. Central laboratory of Physico-chemical Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. bl. 1, 1113 Sofia, Bulgaria
  4. Institute of Polymers, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. bl. 103A, 1113 Sofia, Bulgaria

Abstract

Influence of the electrophoretic suspension on the previously deposited film in multilayer Organic Based Devices (OBDs) in a case when both polymers are soluble in the same organic solvent was investigated. The problem with dissolution of the underlying layer was avoided by using electrophoretic deposition technique. The OBD consists of ITO bottom electrode, spin coated polyvinylcarbazole (PVK) film, electrophoretically deposited (EPD) poly[2-methoxy-5-(3,7-dimethyloctyloxy)-1,4- phenylene vinylene] (MDMO-PPV) film and aluminum top electrode. The EPD deposition, carried out at a constant current, requires continuous increase of the voltage between the electrodes. In this way the decreased deposition rate caused by the decreased concentration of the material in the suspension and the increased thickness of the film deposited are compensated. A comparison of AFM images of untreated and treated in the electrophoretic suspension films shows that the treatment causes an appearance of holes surrounded by high edged rings, raised over the film surface. The current voltage (I-V) characteristics recorded from ITO|PVK|Al structures with treated in the electrophoretic suspension PVK films show that the holes formed in the film did not leads to a short connection between the electrodes, probably due to the sharp walls of the raised rings around the holes. I-V characteristics measured on diode structures show that the introduced PVK hole transport layer increases the device current. The processes need more optimization to get an application level of electroluminescent and photovoltaic OBDs preparation..

Keywords

Thin films, Organic based devices, Polyvinylcarbazole, Poly(p-phenylene vinylene).

Submitted at: Aug. 2, 2010
Accepted at: Sept. 15, 2010

Citation

D. MLADENOVA, D. DIMOV, D. KARASHANOVA, S. BOYADZHIEV, T. DOBREVA, D. BUDUROVA, V. SINIGERSKY, I. ZHIVKOV, Influence of the electrophoretic suspension on the underlayers in organic based devices, Journal of Optoelectronics and Advanced Materials Vol. 12, Iss. 9, pp. 1952-1956 (2010)