Properties of Organic Semiconductors

Roginski, S. Z., Sakharov, M. M. Catalytic Properties of Organic Semiconductors. Russ. 

Chen, H.Y. and Chao, L, Effect of perfluorination on the charge-transport properties of organic semiconductors Density functional theory study of perfluorinated penta-cene and sexithiophene, Chem. Phys. Lett, 401, 539, 2005. 

Most of the interest in OFETs stems from the low thermal budget required to fabricate these devices and their high degree of mechanical flexibility. These characteristics follow from two basic properties of organic semiconductors ... 

Fig. 29 a Top contact and b bottom contact field-effect transistor structures for determination of charge-transport properties of organic semiconductors, c Typical output characteristics and d transfer characteristics of an organic field-effect transistor with Spiro-TAD 61 as active material (measurements by T.P.l. Saragi)... 

Conductivity in organic systems is broadly divided into conductivity in crystals or films and conductivity in polymers. Single crystals without impurities are well suited for investigating the intrinsic charge transport properties of organic semiconductors. 

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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