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Thin Film Fabrication Process Using Liquid Crystallinity

In the case of crystalline thin films fabricated by a solution process, it is difficult to fabriacte flat and uniform crystalline thin films of low molecular weight materials with highly crystalline ordering because recrystallization always occurs randomly as the solvent volatilizes. On the other hand, using amorphous materials and polymer materials that do not crystallize and easily produce flat and uniform thin films, but high mobility cannot be achieved due to low order of moleculs. By utilizing liquid crystal properties, crystalline thin films with uniform molecular orientation, high flatness, and high crystallinity can be fabricated using conventional solution process methods. By using liquid crystalline films as a precursor state, it is possible to easily fabricate crystalline films with flatness and high crystallinity. Flat and uniform crystalline thin films of terthiophene and benzothienobenzothiophene (BTBT) liquid crystals can be realized using the spin coating method, a simple solution process method.
H.Iino et al. Adv. Mater. (2011).

Flat and uniform polycrystalline thin films can be easily formed by dip coating at the temperataure of liquid crystal phase. Even at a high withdrawing speed (2.4m/min) from the solution of liquid crystalline phenyl-benzothienobenzothiophene (Ph-BTBT-10), highly flat polycrystalline thin films can be easily produced by film formation at the temperature of liquid crystal phase. It was found that polycrystalline thin films with a size of about 10 cm square can be fabricated.
Hao Wu et al. ACS Appl. Mater. Inter. (2020).

We are currently researching a new printing method utilizing liquid crystalline properties for patterning of organic semiconductors, which is essential for coating films on flexible substrates and integration of transistors.

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