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Field Effect Transistors
Organic semiconductors show both p- or n-channel or ambipolar conduction depending on their chemical composition. The narrow bandwidth of organic semiconductors makes charge carriers in these materials far more sensitive to their environment than in conventional inorganic semiconductors, particular in n-type materials. Small conjugated molecules, such as the acene family, applied in OFETs have demonstrated that these materials achieve higher mobility when presenting high degree of structural ordering, like in single crystals. This should result in a better device performance and, in addition, it also allows the study of intrinsic electronic properties. The focus of this research has been in using new materials in single-crystal OFET.
This approach has enabled very stimulating results, which have pushed forward some fundamental problems of organic materials. Such an example is the use of a new molecular compound based on a perylene derivative in a single-crystal OFET that achieved very high electron mobility, with excellent FET characteristics in air (Fig.1).
Another example is air-gap FETs with tetramethyltetraselenafulvalene, which were built in and used to demonstrate the occurrence of intrinsic transport. This is the second organic material presenting intrinsic transport and the best at lower temperatures (40K) (Fig 2).
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Fig. 1 |
Fig. 2 |
