Molecular Orientation and Electromagnetic Properties of Perhydrogenated and Perfluorinated Copper Phthalocyanine Thin Films

Abstract

X-ray diffraction (XRD) data shows lattice planes with a spacing of 12.8 Å for copper phthalocyanine (CuPc) thin films. Comparison between the XRD patterns of CuPc powder and thin films suggests that the molecules are oriented along the (100) lattice plane nearly perpendicular to the substrate. The XRD data of the perfluorinated phthalocyanine (F16CuPc) thin film indicate a similar structure to that of CuPc, but with a wider lattice spacing of 14.6 Å. Angular variations of the line position (g-value) of ESR spectra reveal tilt angles of 39 and 34° for the CuPc and F16CuPc thin films, respectively, and the same deviation angle of 24°. This indicates a cone-shaped orientation of CuPc and F16CuPc with similar tilt and deviation angles. The ESR linewidths of both films show angular variation, indicating one-dimensional spin-chain interactions in both the CuPc and F16CuPc thin films. Organic thin-film transistors (OTFTs) with CuPc and F16CuPc films are tested for their suitability as channel layers. The OTFTs with a CuPc film exhibit conduction with holes as carriers, and have a field-effect mobility of 2.6 ×10-5 cm2 V-1 s-1 and an on/off ratio of 10 in the accumulation mode. The OTFTs with F16CuPc films exhibit conduction with electrons as carriers (n-type), and have a field-effect mobility of 2.0 ×10-4 cm2 V-1 s-1 and an on/off ratio of 2.4 ×104 in the accumulation mode.