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Organic field-effect transistors (OFET) based on octamethylenetetrathiafulvalene (OMTTF) and the t-butyl derivative are investigated. The parent OMTTF shows poor transistor performance owing to the flat molecular arrangement, but the t-butyl substitution realizes standing molecular arrangement and high OFET performance. The tetracyanoquinodimethane (TCNQ) complex of OMTTF exhibits n-channel properties despite the strong donor ability of OMTTF.

The molecular orientation and the electronic structure at molecular donor/acceptor interfaces play an important role in the performance of organic optoelectronic devices. Here, we show that graphene substrates can be used as templates for tuning the molecular orientation of pentacene (PEN), selectively driving the formation of either face-on or edge-on arrangements by controlling the temperature of the substrate during deposition. The electronic structure and morphology of the two resulting C60/PEN heterointerfaces were elucidated using ultraviolet photoelectron spectroscopy and atomic force microscopy, respectively. While the C60/PEN (edge-on) interface exhibited a vacuum level alignment, the C60/PEN (face-on) interface exhibited a vacuum level shift of 0.2 eV, which was attributed to the formation of an interface dipole that resulted from polarization at the C60/PEN boundary.

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Low-pressure discharges excited by a microwave ( f = 2.45 GHz) supplemented with a static magnetic field are studied for possible use as new electrodeless Light sources. When the magnetic field strength is increased over the range of the electron cyclotron resonance (ECR), the light intensity emitted from the mercury lamp is more than 4.6 times that at B = 0 in highpower operation of the microwave. In the case of low-power operation of the microwave, the light intensity measured at the ECR point is increased to about three times that at B = 0, although the total maximum intensity of the emitted light is weaker than that in high-power case. The mechanism of the increment of light intensity in the high-power case is discussed with using the model of a helicon wave excitation.