Role of Charge–carrier Trapping in Organic Optoelectronic Devices

This review aims to analyse the impact of charge carrier trapping processes on the performance of organic optoelectronic devices, particularly organic light emitting diodes. The importance of this subject stems from the fact that the trapping processes are unavoidable in organic semiconductors. The photogeneration, transport and recombination of charge carriers are affected by the presence of traps. In the introduction, after a brief presentation of the basic equations describing the kinetic of charge carrier trapping in semiconductors, the working principles of the organic light emitting diodes, organic photovoltaics and organic thin film transistors will be described in elementary terms. Specifically, the reason for the trapping processes and how they manifest themselves in such devices will be investigated. In the second part of the paper, the most important experimental techniques used for the detection and the characterization of the charge carrier traps in organic semiconductors will be described. Finally, in the last part of the review, the state–of–the art research on the origin, the mechanisms and the role of the trapping phenomena observed experimentally in working organic optoelectronic devices, will be presented