Abstract
The performance of organic electronic devices depends strongly on the quality of the semiconductor used, and the transport process, in particular is greatly affected by the defect states of the material. Knowledge of trapping parameters is therefore of prime importance for studying organic devices. While defects in conventional semiconductors are well known and can be more or less controlled during processing, the formation of defects in organic materials is still not well understood, and consequently, it is difficult to control the defect states in organic devices. For defects that are electrically active or traps, techniques such as thermally stimulated currents, impedance spectroscopy, or deep level transient spectroscopy have been successfully used for determining the corresponding parameters (density, energy level, capture cross section). In this work, we review some fundamental aspects of trap analysis in organic devices by highlighting their role in the charge transport process in these materials. We present updated data from trap studies in polyfluorene derivative based diodes and we address specific problems in analyzing traps in polymers and organic semiconductors. (Β© 2008 WILEYβVCH Verlag GmbH & Co. KGaA, Weinheim)