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Observation of electron injection in an organic field-effect transistor with electroluminescence

Ohshima Y., Kohn H., Lim E., Manaka T., Iwamoto M.

Materials Science Poland

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2009

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Vol. 27, No. 3

719--726

EN

A tetracene field-effect transistor (FET) with Au source and drain electrodes showed p-channel type behaviour, where the injected holes were the main carriers. Application of an ac electric field to the source electrode, while drain and gate electrodes were grounded, induced electroluminescence (EL) around the source electrode that was caused by alternating electron and hole injection. This result indicated that electron injection into tetracene was possible from a metal with a high work function such as Au. The application of an ac voltage superposed on a dc voltage showed that electron injection was assisted by the space-charge field that originated from holes accumulated around the source electrode.

2

Circular dichroism and electroluminescence of poly(diacetylene) film with chirality

Kohn H., Fukada M., Ohshima Y., Manaka T., Iwamoto M.

Materials Science Poland

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2009

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Vol. 27, No. 3

727--734

EN

By applying only circularly polarized light (CPL) irradiation to evaporated achiral diacetylene (DA) monomer film during its photopolymerization process, we prepared poly(diacetylene) (PDA) films that show circular dichroism (CD). The left- or right-handed chirality was induced in the polymerized PDA films by the left- and right-CPL irradiation. We studied physical properties of the prepared PDA films, including their electrical and optical properties. The induced chirality in PDA films was not destroyed after annealing at 353 K for 10 min, whilst their blue-phase was changed into a red one. The intensity of the CD signal was dependent on the substrate temperature employed for the monomer deposition. Electroluminescence was found to be enhanced with the polymerized PDA films installed as an active layer of organic field-effect transistors.

3

Ambipolar injection into pentacene field effect transistor observed by time-resolved optical second harmonic generation imaging

Manaka T., Nakao M., Lim E., Iwamoto M.

Materials Science Poland

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2009

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Vol. 27, No. 3

709--717

EN

Ambipolar carrier injection from gold electrode into pentacene was investigated by time-resolved optical second harmonic generation (TRM-SHG) imaging. Smooth hole injection is verified by rapid decrease of the SHG intensity at the electrode edge, indicating the absence of an injection barrier. In contrast, TRM-SHG results clearly indicated the presence of electron injection from the high-work function metal into the electrode, though after injection electrons were trapped in the channel and could not contribute to the conduction. Transient electric field distribution due to the injected holes and electrons were evaluated based on the SHG intensity distribution.