Spray printed crystals for printable organic electronics

A team of researchers from the University of Surrey and National Physical Laboratory is said to have demonstrated a low cost, scalable spray-printing process to make high quality isolated organic single crystals.

A new class of crystalline materials, or organic semiconductors, can also be grown as single crystals – but using solution-based methods at room temperature rather than the high temperatures needed for silicon-based crystals. This opens up the possibility of large scale production of inexpensive electronics, targeting numerous applications, including field effect transistors, light emitting diodes, medical x-ray detectors and miniature lasers. The method is suitable for a variety of semiconducting small molecules, which can be dissolved in solvents to make semiconducting inks, and then deposited on virtually any substrate. The key aspect is claimed to be in combining the advantages of antisolvent crystallisation and solution shearing. The crystals’ size, shape and orientation are then controlled by the spray angle and distance to the substrate which govern the spray droplets’ impact onto the antisolvent’s surface. “With a new class of organic semiconductors based on carbon atoms, we can spray-coat organic inks onto anything, and get more or less the right size of crystals for our devices right away,” said Dr Maxim Shkunov from the Advanced Technology Institute at the University of Surrey. “The trick is to cover the surface with a non-solvent so that semiconductor molecules float on top and self-assemble into highly ordered crystals. We can also use light emitting molecules to make lasers, for example, – something you can’t do with traditional silicon. This molecular crystals growth method opens amazing capabilities for printable organic electronics.”

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