Photoconductive properties and mesomorphic phase transition behavior of octa long-chain n-alkylthio substituted phthalocyanine

Abstract

Mesogenic phthalocyanines are particularly attractive materials for studies of the photonic and electronic properties in mesophase. In this work, the dc photo- and dark-conductivity of 2,3,9,10,16,17,23,24-octa(octadeclythio)phthalocyanine (C_<18>SPcH_2) has been studied with the phase transition behavior. The temperature dependence of the dark- and photo-currents (for positive and negative electrode illuminations) has been measured for a symmetrical cell (ITO/C_<18>SPcH_2/ITO) in the temperature range from 25℃ (crystal) to 245℃ (isotropic liquid). The steady state dark- and photocurrents increase with the first phase transition from a room temperature crystal on heating. At the phase transition to hexagonal columnar mesophase, dark- and photo-currents were once drastically decreased but gradually increased until the isotropic phase.