Oligothiophenes transport properties

Poly- and oligothiophenes are generally p-type (hole-transporting) semiconductors. In thiophene-S,S-dioxide (98AM551 98JOC5497), this modification results in de-aromatization of the thiophene unit and increases the electron affinity and electron-transport properties of the... 

A maximum luminance value of about 90000 cd/m at 1300 mA/cm was reached for 13 and of about 90000 cd/m at a similar current density for 2. The good performance of the devices was likely to be related to a much better balance of electron- and hole-transport properties than that achieved with linear or V-shaped oligothiophene-S,S-dioxides. 

Afzali, A., Breen, T.L., and Kagan, C.R., An efficient synthesis of symmetrical oligothiophenes Synthesis and transport properties of a soluble sexithiophene derivative, Chem. Mater. 14, 1742-1746, 2002. 

The other aspect is related to the basic studies of the charge-transport processes and mechanisms in the molecular conductive materials. This is because fundamental transport properties such as mobility can be easily defined on these electronic devices. Optical processes can be appropriately dealt with similarly. In this section, we highlight the thin-film electronic devices of FETs and LEDs based on the oligothiophenes in relation to the devices using other organic materials. Details of the fabrication and action characteristics of the devices using those materials can be seen in recent papers and reports. 

We have outlined the synthesis, structural characterization, spectroscopic and electronic features, and charge transport properties as well as electronic device applications of the molecular conductive materials of polythiophenes and oligothiophenes. These materials have been characterized and described as those comprising thiophene ring units and were shown to exhibit unique structural and electronic properties as a function of the number of those units (oligomer to polymer). 

One essential parameter for charge transport properties in solid state oligothiophenes is the distance between molecules. In the a-3T crystal, the shortest S- -S distances measured by Van Bolhuis et al. are those between the outer sulfur atoms of adjacent identical molecules, i.e. 3.690 A and 3.711 A respectively [51]. All other S- -S distances are 4.1 A or longer. 

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