M. G. Harrison, J. Gruner and G. C. W. Spencer.
Synthetic Metals 76:1-3 (1996) p71-75 .
rectification, cells electroluminescence, diodes, 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-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 Angstrom, 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 pi-pi* 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.
If you cannot find any of these papers, drop me a line for a reprint...
Mark Harrison firstname.lastname@example.org, Marburg, May 3, 1998