A thin-film transistor (TFT) with high carrier mobility has been fabricated using precursor-route poly(2,5-thienylenevinylene) (PTV) as semiconductor. The carrier mobility has been determined to be 0.22 cm2/V s, which is in the same level of that of amorphous silicon TFT. It has also been made clear that the carrier mobility is linearly proportional to the conversion ratio from the insulated precursor polymer to π-conjugated PTV. The π-conjugation length is crucial to obtain high carrier mobility in π-conjugated polymer TFT.

The optical and structural properties for 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) films deposited on Au-coated substrates at the various growth temperatures by the organic molecular beam deposition (OMBD) method have been studied. The planar PTCDA molecules were oriented almost parallel to the substrate surface in the films deposited at the growth temperature of -160° C. Orientational disorder of the molecular planes occurred especially in the films grown at higher substrate temperatures. These films had basically large anisotropy of refractive indices which were evaluated by the prism attenuated total-reflection (ATR) method. The anisotropy of indices decreased for the film grown at the substrate temperature of 100° C. The optical anisotropy has been understood in terms of the molecular orientation.

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We have developed highly crystallized n-type microcrystalline Si layers as window layers for rear emitter Si heterojunction solar cells. We introduce a seed layer between an n-type microcrystalline Si layer and an intrinsic amorphous Si layer to improve the crystallinity of the n-type microcrystalline Si layer. By using this stacked layer instead of an n-type amorphous Si layer, the contact resistance between the n-type thin layer and In2O3:H is reduced without Al-doped ZnO. As a result, we obtain a high short-circuit current and a high fill factor simultaneously, and achieve a solar cell efficiency of 23.43%.

The field-effect transistor has been fabricated, where polythiophene works as a semiconductor and a couple of polypyrrole layers act as a source and/or a drain electrode. The modulation ratio of the channel current with gate voltages has reached ca. 105, which is the largest one among organic FETs. This large modulation has been attributed to the depression of the channel current at no gate bias. It has been elucidated that the depression is caused by the barrier against hole transport formed inside the polythiophene layer and near the interface with polypyrrole.

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