Toward n-channel organic thin film transistors based on a distyryl-bithiophene derivatives

Solution and solid-state properties of two new perfluoroalkyl end-substituted analogues of distyryl-bithiophene (CF₃-DS2T and diCF₃-DS2T) are presented. Vacuum deposited thin films were investigated by atomic force microscopy, X-ray diffraction, and implemented as active layers into organic thin film transistors. While physicochemical measurements in solution suggest a preferential hole injection and transport inside CF₃-DS2T and diCF₃-DS2T films, electrical measurements performed under high vacuum show that CF₃-DS2T behaves as n-type semiconductor while no charge transport was measured in diCF₃-DS2T. The results highlighted the importance of substituents on conjugated backbone and on the resulting fine ordering in solid state to control the charge transport.     

Characterization of in‐plane structures of vapor deposited thin‐films of distyryl‐oligothiophenes by grazing incidence x‐ray diffractometry

The in‐plane structures of vapor deposited ultrathin films of distyryl‐oligothiophenes (DS‐2T) on SiO₂ substrate were characterized by grazing incidence x‐ray diffractometry (GIXD). Two polymorphs, low‐temperature and high‐temperature phases, were identified, and the two dimensional unit cell parameters were determined for each polymorph. The polymorphism depends on substrate temperature and film thickness. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)