Field-effect transistors based on tetraphenyldipyranylidenes and the sulfur analogues

The field-effect transistors based on tetraphenyldipyranylidenes and the sulfur analogues were studied for their applications as flat-panel displays, electronic papers, and chemical sensors and as they have advantages of low cost, large-area fabrication, and flexibility. The UV based absorption spectra in dichloromethane showed intense absorptions in the visible region because of the extended conjugation. The FET devices were fabricated with bottom contact configuration and all of the compounds showed p-type FET characteristics in a vacuum, with an increase of the size of halogen atom, the mobility decreased gradually except for iodine. The parent compound 1a and its sulfur analogue 2a afforded good performance p-type FETs, as halogen substituents and alkyl groups were introduced to the phenyl group of la to increase the stability and solubility.