A comprehensive structural and electrical characterization of solution-processed blend films of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) and poly(alpha-methylstyrene) (PaMS) was performed to understand and optimize the blend semiconductor films, which are very attractive as the active layer in organic thin-film transistors (OTFTs). Our study, based on careful measurements of specular neutron reflectivity and grazing-incidence X-ray diffraction, showed not only the important segregation phenomenon of TIPS-pentacene to the air surface but also a surprising effect of the molecular weight of the PaMS insulator on the TIPS-pentacene segregation and crystallization at the solid substrate, which is most critical to the charge transport in solution-processed OTFTs. This new finding led to the preparation of the TIPS-pentacene/PaMS blend active layer with superior functional properties over those of neat TIPS-pentacene, exhibiting high field-effect mobility, high on/off ratio and low threshold voltage.
Citation: Journal of the American Chemical Society
Pub Type: Journals
organic semiconductor, polymer thin film, neutron reflectivity