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

• Published in: physica status solidi (b) Vol. 255; no. 4
• Main Authors: Ueda, Hiroyuki, Takeuchi, Keita, Terada, Ryo, Kikuchi, Akihiko
• Format: Journal Article
• Language: English
• Published: 01.04.2018
• Subjects: Alq3; electrospray deposition; ionic liquids; organic single crystals
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.201700351

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 Alq3 single crystals were investigated at 25 °C under atmospheric pressure in a nitrogen atmosphere. Using the proposed method, aggregated small crystals of less than 10 μm, rhombic plate‐like crystals with diagonal lengths of 50 μm, and hexagonal plate‐like crystals of 100 μm were precipitated when the solution supply rates (supply times) were 8.0 (90), 4.0 (180), and 2.0 μl min−1 (360 min), respectively. Alq3 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 2.0 μl min−1 for 16 h, large hexagonal plate‐like crystals with a diagonal length of about 400 μm are obtained, which are among the largest plate‐like Alq3‐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. A new organic‐single‐crystal growth technique is described that uses a thin ionic liquid film as the crystal growth field and electrospray deposition as the material supply method. A large plate‐like single crystal (400 μm in diagonal length) of Alq3, which is a difficult to form thin‐film crystal, is grown at room temperature under atmospheric pressure. The effects of solute supply rate and liquid layer thickness on the crystal precipitation are investigated.