Stability of the interface between indium-tin-oxide and poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) in polymer light-emitting diodes

Applied Physics Letters - Tập 77 Số 14 - Trang 2255-2257 - 2000
M. P. de Jong1, L.J. van IJzendoorn1, M.J.A. de Voigt1
1Centre for Plasmaphysics and Radiation Technology, Department of Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands

Tóm tắt

A cause for degradation of polymer light-emitting diodes is the oxidation of the polymer by oxygen diffusing out of the indium-tin-oxide (ITO) anode. This problem can be solved by the introduction of an organic hole-injecting film, poly-(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS), between the ITO and the emissive polymer. Indeed, a dramatic improvement of the lifetime and also the luminous efficiency has been observed. However, our Rutherford backscattering (RBS) studies show that the ITO/PEDOT:PSS interface is not stable. In as prepared glass/ITO/PEDOT:PSS samples 0.02 at. % indium was found in the PEDOT:PSS film. Annealing in a nitrogen atmosphere at 100 °C during 2500 h increased the indium concentration to 0.2 at. %. Upon exposure to air much faster degradation of the ITO/PEDOT:PSS interface was observed; after several days in air the amount of indium reached a saturation concentration of 1.2 at. %. The degradation of the interface can be explained by etching of the ITO due to the strong acidic nature of PEDOT:PSS.

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Applied Physics Letters

Tập 77 Số 14

2255-2257

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