Electrical properties organic semiconductors, transport

Controlling the chemistry and physics of the dielectric-semiconductor interface is essential to controlling and optimizing the performance of organic electronic devices. There are two main issues associated with the dielectric-semiconductor interface (1) the electrical properties of this interface, which are essential to the reliability, stability, and threshold voltage and (2) the chemical/mechanical properties of the interface, which relate to the ability to orgaiuze the semiconductor layer for efficient charge transport. 

F. Yakuphanoglu, R. Mehrotra, A. Gupta, and M. Munoz, Nanofiber organic semiconductors The effects of nanosize on the electrical charge transport and optical properties of bulk polyanilines, J. Appl. Polym. Sci, 114, 794-799 (2009). 

In conducting polymers, the extra carriers added upon doping are able to drift under an applied electrical field. In semiconducting polymers, no carriers are available except those thermally excited across the gap. However, negative (positive) carriers can be injected into the material by metallic contacts when the barrier between the metal work function and the LUMO (HOMO) molecular levels is overcome. Then, the injected carriers can move inside the semiconductor if a bias field is applied. Injection of carriers and their transport is a fundamental issue for all electronic devices and transistors in particular. In the following, main transport properties of organic semiconductors (both small molecules and polymers-based) used as active materials in transistors will be reviewed. 

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