Leuco dye indicates the reversible coloring reaction with acidic compounds (called developer) having long-chain moiety. In order to clarify the structural change between colored state and decolored one of this system, X-ray diffraction (XRD) measurements and transmission electron microscope (TEM) observations were performed. It was found that mixture of leuco dye and developer took different layered structures between colored and decolored state. This structural change shows intercalation and deintercalation of leuco dye occur in the reversible coloring process. The mechanism of coloring/decoloring reaction of leuco dye with long-chain molecule is proposed.

The highest carrier mobility of polydiacetylene (PDA) thin films in field-effect transistors has been limited to less than 0.8 cm2 V-1 s-1, although the main chain conduction should show higher carrier mobility potentially. We revealed that the cause of the low carrier mobility is due to the presence of local upheaval regions generated by the volume change through the polymerization process of diacetylene monomers. In order to suppress the occurrence of the upheaval regions, we found that electron beam (EB) irradiation is effective, resulted in the highest carrier mobility of µmax = 3.8 cm2 V-1 s-1.

A double layer of dianthratetrathiafulvalene (DATTF) and fullerene (C60) on an n++-Si wafer pretreated with n-octyltrichlorosilane exhibited a high electrical conductivity of σ= 0.12 S/cm and was used as source–drain electrodes in organic field effect transistors (OFETs). A simplified OFET device architecture composed of an organic semiconducting active layer and an organic electrode layer was easily fabricated by successive vacuum deposition of organic donor and acceptor layers. It was confirmed that this device configuration is applicable for both p- and n-type FET operation.

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