Dependence of the dielectric properties of organic light-emitting diodes with a PTFE hole-injection layer on the applied voltage

초록

The dependences of the dielectric properties of organic light-emitting diodes on applied AC voltage were studied in a structure of indium tin oxide(ITO)/hole injection layer, polytetrafluorethylene (PTFE)/Alq(3)(tris(8-hydroxyquinoline)aluminum)/Al. The hole-injection material PTFE, which is a fluoric-system polymer, was deposited at a deposition rate of 0.1 similar to 0.2 angstrom/s to a thickness of 2 nm and the Alq(3) was deposited at a deposition rate of 1.3 similar to 1.5 angstrom/s under high vacuum (5 x 10(-6) Torr) to a thickness of 100 inn. To investigate the dielectric properties of these devices, we measured the complex impedance, which showed that the impedance decreased as the applied voltage was increased and that the dielectric loss exhibited a peak at a certain voltage. A Cole-Cole plot of the impedance was plotted and analyzed. As the applied voltage was increased, the radius of the Cole-Cole plot decreased. The interface resistance between the ITO and the double layer was about 35 Q in the device with a 100-nm-thick Alq(3) layer.

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