Carrier Transport Investigation on Organic Semiconductor by Electrical DC and AC Measurements: the Case of Alq₃

Abstract

In the present work, the nature of the electrical mechanism for carrier transport in Alq3 is studied by current-voltage measurements and broadband dielectric spectroscopy. The d.c. currentvoltage characteristics at low applied electrical field exhibits a classical “N” shape due to interfacial states located at metal-organic interface, but tend to disappear when successive higher forward bias is applied. Using dielectric spectroscopy it is possible to observe that the main relaxation peak shifts to a higher frequency with the increase of the applied d.c. voltage (from approximately 100 Hz with 0 V d.c. bias to approximately 400 Hz with 6 V d.c. bias) indicating a semiconductor structure change. The logarithmic Z’’ vs. Z’ plot has a slope about 0.7 that decreases to 0.5 with the increasing applied d.c. voltage, reaching a classic Debye relaxation. An attempt to correlate with some structural changes is made.

Effect of field cycling on the ac and dc properties of Alq3 device

“…In particular, the effect of electrical field application appears to be the most important [4]. Therefore, it is important to study the influence of the electrical field application in the global electrical device properties.…”