Investigations of organic electroluminescent diodes by impedance spectroscopy, photo-impedance spectroscopy and modulated photovoltage spectroscopy
We have fabricated single-layer organic electroluminescent diodes with poly( para-phenylene vinylene) (PPV) and poly(2-methoxy-5-ethyl(2′-hexyloxy) para-phenylene vinylene) (MEH-PPV), using indium-tin oxide (ITO) or semi-transparent gold as hole-injecting anodes and aluminium or calcium as electron-...
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Published in | Synthetic metals Vol. 76; no. 1; pp. 71 - 75 |
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Main Authors | , , |
Format | Journal Article Conference Proceeding |
Language | English |
Published |
Lausanne
Elsevier B.V
1996
Amsterdam Elsevier Science New York, NY |
Subjects | |
Online Access | Get full text |
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Summary: | We have fabricated single-layer organic electroluminescent diodes with poly(
para-phenylene vinylene) (PPV) and poly(2-methoxy-5-ethyl(2′-hexyloxy)
para-phenylene vinylene) (MEH-PPV), using indium-tin oxide (ITO) or semi-transparent gold as hole-injecting anodes and aluminium or calcium as electron-injecting cathodes. We measured impedance spectra of the devices, both in the dark and under illumination. We observed no evidence for depletion layers. Some devices show a thin highly resistive barrier layer, of width about 100 Å, independent of bias. From measurements of the modulation in the open-circuit photovoltage across the device, in response to chopped monochromatic light incident on the ITO electrode, we resolved two distinct spectral features close to the π-π
* energy of the polymers: a narrow response in the low-energy tail of the absorption spectrum and a much broader response which follows the absorption spectrum. Studies of bias dependence and frequency dependence also indicate that the two spectral features have different physical origins. |
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ISSN: | 0379-6779 1879-3290 |
DOI: | 10.1016/0379-6779(95)03422-G |