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The processing characteristics of organic semiconductors make them potentially useful for electronic applications where low-cost, large area coverage and structural flexibility are required. This critical review gives a general introduction about the current standing in the area of OFETs focusing on the new processable small molecules that have been recently reported for their use as organic semiconductors. A general description of the OFETs device operation and the transport mechanisms that dominate organic semiconductors is provided, followed by an overview of the strategies and materials employed to fabricate p-type, n-type and ambipolar OFETs. Some new tendencies and applications that are currently being developed employing OFETs are also described, such as the preparation of electronic paper, sensors or light emitting transistors (85 references).

Recently, it was reported that crystals of the organic material dithiophene-tetrathiafulvalene (DT-TTF) have a high field-effect charge carrier mobility of 1.4 cm(2)/(V x s). These crystals were formed by a simple drop-casting method, making this material interesting to investigate for possible applications in low-cost electronics. Here, organic single-crystal field-effect transistors based on materials related to DT-TTF are presented and a clear correlation between the crystal structure and the electrical characteristics is observed. The observed relationship between the mobilities in the different crystal structures is strongly corroborated by calculations of both the molecular reorganization energies and the maximum intermolecular transfer integrals. The most suitable materials described here exhibit mobilities that are among the highest reported for organic field-effect transistors and that are the highest reported for solution-processed materials.