2.Innovative printing processes
Development of Innovative Printing Processes for Flexible Devices
The crucial advantage of organic electronic materials is that they should be most suitable for the use in printing processes that are the most promising way to realize the flexible electronics devices. However, it is also true that conventional printing processes in their present forms cannot be applied to the thin-film patterning or to wiring since the high quality semiconductor films are required in the electronic devices. We are working to develop innovative printing processes for organic semiconductors, conductors, and ferroelectrics by fully utilizing the functionality of organic materials such as high solubility and a self-organizing nature.
Topics presented so far：
Inkjet Printing of Single-crystalline Organic Semiconductor Films
We have developed a novel inkjet-printing technique to obtain exceptionally uniform single-crystal or polycrystalline thin films manufactured from soluble organic semiconductors.
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2.Inkjet Printing of Molecular Conductor Films
We have developed a double-shot inkjet printing method to fabricate patterned thin films from highly-conductive organic films. We have found that organic transistors equipped with an inkjet printed source and drain electrodes exhibit sharp on/off switching.
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Adv. Mater. 19, 3248 (2007), Appl. Phys. Lett. 95, 223304 (2009), Thin Sol. Films 518, 14, 3988 (2010).
3.Simulation of Droplets on Hydrophilic/Hydrophobic Patterned Surfaces
We developed a new simulation method for the droplets printed onto the substrate with hydrophilic/hydrophobic patterns, as used for inkjet printing of fine circuits.
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4.Control of Grain Size in Polycrystalline Organic Semiconductor Films
We have ascertained that the grain size of polycrystalline organic semiconductor films made from dibenzotetrathiafulvalene (DBTTF) depends on the surface energy of the gate dielectric layers. From the characteristics of organic transistors composed of polycrystalline films, we found that the sharpness of on/off switching and the chemical stability are critically dependant on grain size.
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5.Thin-Film Growth of Organic Semiconductors with a Non-Layered Packing Motif
It is known that most high-mobility organic semiconductor films are grown with a layered packing motif. We found that hexamethylenetetrathiofulvalene (HMTTF) organic semiconductor films are grown on top of plastic films with a non-layered packing motif, and that three-dimensional brickwork stacks afford high-mobility (6.9 cm2/Vs) organic thin-film transistors.
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