The mesogenic phthalocyanine, C6PcH2 (Fig.1), is a promising organic material with a high hole mobility of 1.4 cm 2 V-2 s-1[1]. It tends to form a columnar structure and is processable in solution. The solution processed thinfilm of C6PcH2 has a polycrystalline structure orienting in random directions, however, a molecular-aligned thin-film must be appropriate for realizing high performance devices. This work reports a method to control the alignment of C6PcH2 by applying the principle of crystal growth.

The effects of solvent vapor on spin-coated films of a polymorphic phthalocyanine derivative were investigated. Growth of single crystal films via redissolving organic films under solvent vapor was revealed by in situ microscopic observations of the films. X-ray diffraction measurement of the films after exposing to solvent vapor revealed the phase transition of polymorphs under solvent vapor. The direction of crystal growth was clarified by measuring the crystal orientation in a grown monodomain film. The mechanism of crystal growth based on redissolving organic films under solvent vapor was discussed in terms of the different solubilities of the polymorphs.

Spin-coatedfilms of a mesogenic phthalocyanine derivative, 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH 2 ), with macroscopic alignment of molecular stacking structure were obtained by processing in liquid-crystal phase of C6PcH 2 . The column axis direction of the hexagonal columnar structure of C6PcH 2 was determined by microscopic observation and polarized optical absorption measurement and was uniform in the millimeter-scale area. Highly ordered molecular stacking structure in the film, which is similar to the single crystal, was clarified by measurement of molecular tilting angle with respect to the column axis. The origin of the macroscopic molecular alignment during film formation was investigated by taking the process-temperature-dependent properties of the films into consideration.

The polymer blend effect in the fabrication of uniaxially oriented thin films of a mesogenic phthalocyanine, 1,4,8,11,15,18,22,25octahexylphthalocyanine (C6PcH 2 ), by contact freezing was studied. Contact freezing was induced by thermal stimulation to a supercooled liquid crystal state of the mixture of C6PcH 2 and poly(3-hexylthiophene) (P3HT). With the blending of P3HT with C6PcH 2 at an appropriate blend ratio, the cracks observed in a pure C6PcH 2 film disappeared while maintaining the uniaxial alignment of C6PcH 2 . The polymer blend effect was discussed by taking the anisotropic optical absorption and molecular stacking structure in the thin films into consideration.

Polymer blending effects on the properties of the mesogenic phthalocyanine thin films fabricated by heated spin-coating method were demonstrated. The spin-coated films of 1,4,8,11,15,18,22,25- octahexylphthalocyanine (C6PcH 2 ) blended with poly(3-hexylthiophene) (P3HT) were prepared by controlling the temperatures of substrates and solutions with the mixed material, and the morphology and optical property of the fabricated film were studied. In the case of the low composite ratio of P3HT, the wide crack lines found in pure C6PcH 2 films disappeared while maintaining the uniaxial aligned optic axis direction in the large-area with the diameters of exceeding 1 mm. The polymer blend effects were discussed by taking the anisotropic optical absorption and molecular stacking structure in the films into consideration.