Development of aqueous colloidal dispersions of ladder-type polymers for applications in organic field effect transistors

The development of organic semiconductors is an important and challenging topic of the modern microelectronics since they can be applied as active layers in devices combining the advantages of easy processing, low weight, mechanical flexibility and ability of properties-tuning by structural modifications. A spectacular example for these attractive properties are the organic field effect transistors (OFETs) which are highly important components and recently have been a subject to a significant technological development. Particularly attractive candidates for OFET-applications are the semiconducting polymers due to their simple, low-cost solution processing, at low temperatures that enable large-area deposition on broad range of substrates. Typically, the reports of the semiconducting polymers, as of most organic materials, discuss unipolar charge transport. The result are devices, that can operate either in p- or n-channel regime, based on charge transport of holes or el ectrons, respectively. However the availability of both charge transport types is necessary for the realisation of numerous important logic elements, such as p-n junction structures, bipolar transistors and complementary circuits. The research attention so far has been oriented predominantly towards the p-type semiconducting polymers. As a result a significant progress has been marked with the achievement of fieldeffect mobilities of up to 0.05-0.1 cm 2/V·s as reported for the regioregularpoly(3-hexylthiophene) (P3HT) [1]. The n-type semiconducting polymers remain, however, markedly less developed. The reasons are, probably, the lower environmental stability and the higher susceptibility of the negative charge carriers to the presence of defect and impurities [2,3]. Consequently the development of polymers with suitable electron transporting properties is a particularly challenging item for the synthetic chemistry. Recently an interesting solution to this task has been proposed in the form of conjug