Dependence of the Dielectric Properties of Organic Light-Emitting Diodes with a PTFE Hole-Injection Layer on the Applied Voltage

The dependences of the dielectric properties of organic light-emiting diodes on applied AC voltage were studied in a structure of indium tin oxide(ITO)/hole injection layer, polytetrafluorethylene (PTFE)/Alq3(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 ∽ 0.2 Å/s to a thicknes of 2 nm and the Alq3 was deposited at a deposition rate of 1.3 ∽ 1.5 Å/s under high vacuum (5 × 10-6 Torr) to a thicknes of 100nm. 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 los exhibited a peak at a certain voltage. A Cole-Cole plot of the impedance was ploted and analyzed. As the applied voltage was increased, the radius of the Cole-Cole plot decreased. The interface resistance betwen the ITO and the double layer was about 35 Ω in the device with a 100-nm-thick Alq3 layer. KCI Citation Count: 5