We report the crystal and band gap structures of copper(II) phthalocyanine (Cu-Pc) thin films depending on the substrate heating conditions and temperatures. The phase changes of the two alpha- and beta-phases of Cu-Pc thin films due to different heating conditions were observed by using X-ray diffractions and electronic absorption spectra. As the temperatures increased from room temperature to 300 degreesC, the energy gap was changed from 1.8052 to 1.7844 eVand the crystal structure of Cu-Pc thin films was transformed from orthorhombic alpha-phase to monoclinic beta-phase. The orientation of grains depended on the heat-treatment conditions and the temperatures of the substrate during film deposition. The transport properties of Cu-Pc thin films with different grain orientations were studied. (C) 2002 Elsevier Science B.V. All rights reserved.