Defect analysis in organic semiconductors

Organic semiconductors are prone to have electronic traps due to their molecular bonds and structural disorder. Several spectroscopic techniques, e.g. optical, magnetic, etc are available to study defects in these materials. For defects that are electrically active, techniques such as thermally stimulated currents, impedance spectroscopy, or deep level transient spectroscopy have been successfully used for determining the trap parameters (density, energy level, capture cross-section, etc). In this paper, we review some fundamental aspects of trap analysis in organic and polymeric semiconductors by highlighting their role in optical and electrical processes in these materials. We present recent data on the trap study in poly[2-methoxy,5-(2′ethyl-hexyloxy)-1,4-phenylene vinylene] or MEH-PPV for device applications and address specific problems in analyzing traps in this polymer.