Proposal of Organic Single Crystal Growth Method Using Electrospray Deposition and Thin-Film Ionic Liquid

A novel crystal growth technique is proposed that uses a thin ionic liquid film with an extremely low vapor pressure as the crystal growth field, and a solute supplied by electrospray deposition through the surface of the liquid film. The precipitation properties of small molecule Alq(3) single crystals were investigated at 25 degrees C under atmospheric pressure in a nitrogen atmosphere. Using the proposed method, aggregated small crystals of less than 10m, rhombic plate-like crystals with diagonal lengths of 50m, and hexagonal plate-like crystals of 100m were precipitated when the solution supply rates (supply times) were 8.0 (90), 4.0 (180), and 2.0lmin(-1) (360min), respectively. Alq(3) is known to be a material difficult to grow into plate-like crystals, however, when solution was supplied to the ionic liquid at a rate of 2.0lmin(-1) for 16h, large hexagonal plate-like crystals with a diagonal length of about 400m are obtained, which are among the largest plate-like Alq(3)-based crystals ever reported. The proposed crystal growth technique is expected to be beneficial for growing large size plate-like single crystals of various organic materials.