Growth of phthalocyanine doped anthracene crystal using a three-zone furnace by vacuum sublimation method

Abstract

Anthracene is an organic semiconductor extensively investigated over many decades. It finds applications as photoreceptor material, scintillation counter etc. Anthracene is optically active in the UV region of the electromagnetic spectrum whereas H2Pc is active from visible through IR regions. Hence phthalocyanine (H2Pc) doped anthracene crystal formed is expected to be active in the entire region UV–VIS–IR, and the compound material could be a viable alternative for a possible solar cell material. In the present study doped crystal was grown by two methods namely co-crystallization and vacuum sublimation using a special type three-zone furnace. The co-crystals of anthracene and H2Pc were formed using dimethyl sulphoxide as the common solvent, and were subjected to various analysis including electroreflectance method. The electroreflectance method gives the band gap accurately and the calculations show that there is a decrease in the band gap as the concentration of H2Pc increases. Also the doped samples were found to be photo active and hence H2Pc could be used as a suitable dopant to increase the conductivity of anthracene. A special type three-zone furnace is designed to grow H2Pc doped anthracene single crystal. The melting point of anthracene is 217°C while H2Pc decomposes above 550°C, but sublimates around 460°C in vacuum. Anthracene and H2Pc were placed in two side arms of a main stem and the tube is sealed in vacuum. The sealed tube is heated for few days to enhance the growth of a single crystal. The compound crystal is formed along with the main stem at a convenient temperature gradient.