Steady state charge conduction through solution processed liquid crystalline lanthanide bisphthalocyanine films

In-plane electrical characteristics of non-peripherally octyl (C8H17) and hexyl (C6H13) substituted liquid crystalline (LC) double decker lanthanide bisphthalocyanine (LnPc2) complexes with central metal ions lutetium (Lu), and gadolinium (Gd) have been measured in thin film formulations on interdigitated gold (Au) electrodes for the applied voltage (V_a) range of 〖0 ≤ V〗_a ≤100 V. The conduction mechanism is found to be Ohmic within the bias of 〖0 ≤ V〗_a ≤30 V 0≤Va≤30 V while the bulk limited Poole-Frenkel mechanism is responsible for the higher bias. The compounds show individual characteristics depending on the central metal ions, substituent chain lengths and their mesophases. Values of 67.55 μS〖cm〗^(-1) and 42.31 μS〖cm〗^(-1) have been obtained. for room temperature in-plane Ohmic conductivity of as-deposited octyl lutetium (C8LuPc2) and hexyl gadolinium (C6GdPc2) films, respectively while C8GdPc2 films exhibit nearly two orders of magnitude smaller conductivity. On annealing at 80 ̊C, Ohmic conductivities of C8LuPc2 and C8GdPc2 are found to have increased but the conductivity of C6GdPc2 decreases by more than one order of magnitude to 1.5 μS〖cm〗^(-1). For physical interpretation of the charge transport behavior of these three molecules, their UV-visible optical absorption spectra have been studied in the solution and in as-deposited and annealed solid phases. It is believed that both orientational and positional reorganisations are responsible depending upon the size of the central ion and side chain length.