Solution Growth of Rubrene Single Crystals Using Various Organic Solvents

Abstract

To fabricate organic field-effect transistors (OFETs) with high carrier mobility, we attempted to grow 5,6,11,12tetraphenylnaphthacene (rubrene) single crystals from solution and to improve their quality. Investigations into solvents in which rubrene was highly soluble proved that its solubility depended on the presence or absence of aromatic rings and chloro groups rather than on the polarity of the solvents. Rubrene crystals were grown from aromatic solvents, specifically from toluene, p-xylene, and aniline solvents, as well as from 1,2-dichloroethane (DCE) solvent. As a result, rubrene single crystals larger than 1 mm were obtained. Powder X-ray diffraction (XRD) analysis showed that the crystals obtained from the p-xylene and toluene solvents were rubrene, and 1 H-nuclear magnetic resonance ( 1 H-NMR) measurement proved that the crystals had not incorporated the solvent at the detection level. In addition, atomic force microscopy (AFM) confirmed that the rubrene crystals grown from the p-xylene and aniline solvents had flat faces and that the crystal from the p-xylene solvent had monomolecular steps on parts of the surfaces. Rubrene single crystal OFETs with graphite electrodes and parylene as an insulator showed carrier mobilities of $0:75 cm 2 V À1 s À1 .

Optical pump-probe spectroscopy of photocarriers in rubrene single crystals

“…In tetracene, photocarrier generation starts at a photon energy of 3.0 eV, which is ∼0.6 eV higher than the lowest exciton energy (∼2.4 eV). 23 Such differences between rubrene and tetracene suggest that the molecular degrees of freedom due to four phenyl groups might stabilize polarons in rubrene. Further studies are required to fully determine the exciton dissociation mechanism.…”

Growth of thin rubrene single crystals from 1-propanol solvent

“…A means to fabricate rubrene single crystals by a solution process is worth developing for the OFET manufacturing process. In a previous study, we searched appropriate solvents for rubrene crystal growth [10]. Rubrene has tended to be moderately soluble in aromatic solvents such as p-xylene (7 mg/ml at 45 1C) and to be less soluble in alcohol solvents such as 1-propanol (PrOH) (0.1 mg/ml at 50 1C).…”

Growth Mechanism of Large-Size Rubrene Single Crystals Grown by a Solution Technique

“…Unfortunately, like other organic semiconductor materials, the solubility of rubrene is also not good in ordinary organic solvents, which makes it very difficult to grow crystals from the solution. In 2008, Matsukawa et al 9) firstly obtained large-size rubrene single crystals by the solution growth method. The size of the crystals reaches up to 1 mm.…”