Molecular orientation control of phthalocyanine thin film by inserting pentacene buffer layer

The effect of a pentacene buffer layer on the molecular orientation of phthalocyanine (H2Pc) films was investigated by X-ray diffraction analysis, atomic force microscopy, and infrared reflection absorption spectroscopy. The results suggested that the pentacene buffer layer can control the orientation of the H2Pc molecular plane to be parallel to the substrate surface of indium tin oxide (ITO), even though the molecular plane of HPc films without a buffer layer is perpendicular to such ITO substrates. The optical absorbance of the H2Pc film with a pentacene buffer layer was 1.5 times larger than that without a buffer layer. Photovoltaic cells composed of H2Pc and C-60 were fabricated, and the performance of the cells with and without a buffer layer was studied.