The paper describes the use of noise current analysis to sense variations of the microscopic conduction process in organic Light Emitting Diodes and to track their evolution through time. The monitoring of current fluctuations has been made both in time and frequency domain and is of great value when one wants to correlate the conduction properties of the charge carriers and the changes in current flow with the corresponding changes in the microscopic morphology of the organic layers. The method reveals itself to be very effective also in sensing the initial state and the growth of catastrophic degradation of oLEDs in large advance with respect to current monitoring or other techniques. Microscopic damages within the device, as a result of microshorts and/or thermal breakdown, are shown to reveal a neat increase of the white noise component of about three orders of magnitude in the power spectral density, that can therefore be detected with very good time precision. This would allow to study the sources that may give reason of degradation, through structural or spectroscopic investigations for example, before the microscopic damages have sum up to a visible and irreversible macroscopic failure.

Date Published: 27 February 2002
PDF: 7 pages
Proc. SPIE 4464, Organic Light-Emitting Materials and Devices V, (27 February 2002); doi: 10.1117/12.457470

Published in SPIE Proceedings Vol. 4464:
Organic Light-Emitting Materials and Devices V
Zakya H. Kafafi, Editor(s)