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Organic electronic devices (OLED)

Thien-Phap NGUYEN

Organic light emitting diodes (LEDs) now appear as a promising application of conjugated polymers. Indeed, the use of polymers or organic materials as active layer in the LEDs makes it possible to obtain specific properties inaccessible to inorganic LEDs: low mass, flexibility, large active area, high luminosity.

We realize the light-emitting diodes based on polymer and organic material and study the different physico-chemical phenomena involved in the operation of LEDs: characterization of active materials, conduction mechanisms in devices, role of interfaces in charge injections , Structure of these interfaces, and degradation phenomena. Based on the knowledge gained from these studies, we design strategies for improving the performance of diodes and apply them to the study of devices using new materials and new structures. On the one hand, a better understanding of the functioning of the diodes has been gained by the appropriate characterization methods (trapping, conduction, degradation.) On the other hand, improvements in the performance of the devices have been achieved. Characterization and electrical analysis of organic semiconductors to model the conduction and transport processes in the studied electronic devices.

 

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 We demonstrate that the inverted structure (emission by the upper electrode) presents the same phenomena and disadvantages as the conventional structures. 
 

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 We demonstrate also that the use of indium tin oxide films as an anode in the devices poses stability problems due to the decomposition of this oxide upon contact with the polymeric films.A reaction between the materials forms complexes at the interface, facilitating the diffusion of the metal atoms in the active film which deteriorate the transport and emission quality of the devices.

 

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Light-emitting diode based on polyacetylene derivative 

In various organic devices, the determination of defects by thermally stimulated current (CTS) and deep trap spectroscopy (DLTS) techniques made it possible to establish the pattern of the energy bands of the structures, with detailed data on the parameters of Traps. However, no indication of their nature could be obtained, and for this identification we are preparing other experiments at this time.

Participants

Mohammed ZEMMOURI (thesis), Cédric RENAUD (thesis), Hassina DERBAL (thesis), Chih WEN LEE (thesis), Yves JOSSE (Trainee M2)

Collaborations, contracts :

  • Europe Contrat OLLA 2004-2008
  • Toulouse, Strasbourg: Contrat ANR 2005-2008
  • Taipei (Taiwan): Contrat CNRS/NST 2004-2006
  • Autres collaborations : Angers, Le Mans, Madrid (Espagne), Chiao Tung (Taiwan), Sydney(Australie), Hanoï (Vietnam).
Thesis : 
  • Joseph Ip – Juillet 2004 - Réalisation et étude des diodes à base d'un dérivé de PPV : le 4,4'-bis(4-dimethylaminostyryl) benzène (DMASB). Influence des interfaces dur les caractéristiques électriques et phénomènes de transport
  • Sheng Hsiung YANG – Août 2004 - Synthèse et étude des composites (polymère-matériau inorganique) utilisés comme éléments actifs dans les diodes électroluminescentes
  • Lotfi DJEBARRA – mars 2006 -Concept, réalisation et étude des composites polymère-oxyde intégrables au procédé de fabrication des condensateurs de haute performance.
  • Chun Hao HUANG – Juin 2006 -Synthèse et étude des propriétés électro-optiques des polyacétylènes disubstitués.
Publications :
  • A combined experimental and theoretical study on the effect of doping and interface formation on PPV-ether copolymer
    MABROUK, K. ALIMI, P. MOLINIE, T. P. NGUYEN,
    Journal of Physical Chemistry B, 110, 1141-1150 (2006)
  • Stabilization of discotic liquid organic thin films by ITO surface treatment
    S. ARCHAMBEAU, I. SEGUY, P. JOLINAT, P. DESTRUEL, T.P. NGUYEN, H. BOCK, E. GRELET,
    Applied Surface Science 253, 2078-2086 (2006).
  • Defect analysis in organic semiconductors
    T. P. NGUYEN,
    Materials Science in Semiconductor Processing, 9, 198-203 (2006).
  • Study of the interface formed between poly(2-methoxy-5-(2'-ethyl-hexyloxyl)-p-phenylene vinylene) and indium tin oxide in top emission devices.
    T. P. NGUYEN, J. IP, C. RENAUD, C. H. HUANG, C. GUILLEN, J. HERRERO
    Applied Surface Science, 252, 8388-8393 (2006).
  • Self-Assembly Monolayer of Anatase Titanium Oxide from Solution Process on Indium Tin Oxide Glass Substrate for Polymer Photovoltaic Cells
    C. H. HUANG, C. H. HUANG, T. P. NGUYEN, C. H. HSU.
    Thin Solid Films (2006, sous presse).
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