Field oligothiophenes

Poly(3-alkyl-a-thiophene) systems show significant third-order nonlinear susceptibilities ( ) Though, oligothiophenes have been studied for their third-order susceptibilities, accurate third-order optical nonlinearity data obtained by degenerate four-wave mixing or electric-field-induced second harmonic generation (EFISH) are difficult to attain reliably on samples with poor solubility characteristics (92MM1901). 

Fully relaxed single-bond torsional potentials of oligothiophenes 16 (n = 0-2) under the interaction of the parallel external electric field (EF) constructed by point charges have been evaluated with semi-empirical AMI and PM3 calculations <2004SM(145)253>. Consistent evolutions of the torsional potential surfaces have been observed for three lineal oligothiophenes (Figure 43) as the EF increases. In particular, the equilibrium molecular geometries are deformed toward planar conformations, and the torsional barriers around the central bond are elevated. These... 

The performance of OFETs has continuously improved since they were first reported in 1987 [8, 9]. The rate of the progress can be visualized in Figure 14-13, where we have plotted the field-effect mobility of five prominent organic com-pounds as a lunclion of the publication date. The data include one polymer, polythiophene and its derivatives and four small molecules (three oligothiophenes, plus pentacene). Note that the highest mobility of small molecules was reported on single crystals. 

Table 14-1. Typical field-effect mobility (in cm V s ) of unsubstituted and dialkyl-substituted oligothiophenes.

In most of the recent literature on oligothiophenes however, substituted molecules become more and more favoured to those unsubstituted derivates since effects due to poor packing can be excluded much more easily and higher field-effect mobilities are usually easier to obtain. 

Assembly, Structure, and Performance of an Ultra-Thin Film Organic Field-Effect Transistor (OFET) Based on Substituted Oligothiophenes... 

Using DHPT-SC as the semiconductor in OFETs, a field effect mobility of 0.012 cmWs and a current on/off ratio of >10 can be realised, which is among the highest OFET mobilities fabricated achieved with solution-processed oligothiophenes. 

T.J., Building blocks for n-type molecular and polymeric electronics. Perfluoroalkyl versus alkyl-functionalized oligothiophenes (riT n = 2-6). Systematics of thin film microstructure, semiconductor performance, and modeling of majority charge injection in field-effect transistors, J. Am. Chem. Soc., 126, 13859-13874, 2004. 

Kunugi, Y, Takimiya, K., Negishi, N., Otsubo, T. and Aso, Y, An ambipolar organic field-effect transistor using oligothiophene incorporated with two 60 fullerenes, J. Mater. Chem., 14, 2840-2841, 2004. 

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