Mesomorphic behaviors and photoconductive properties of binary systems composed of electron donor and acceptor mesogens

Mesomorphic behaviors and photoconductive properties in the binary mixture composed of electron donor (R10D) and acceptor (R10A) mesogens were investigated in three different phases, i.e. crystalline, liquid crystalline and isotropic liquid phases. Optoelectronic properties for R10DA (R10D:R10A=50:50 mol%) were compared with those of the individual R10D and R10A in the different phases. The magnitude of the short-circuit photocurrent in the ITO/R10DA/ITO symmetrical sandwich cell showed the effective improvement in SmA phase compared with one in crystalline phase. These experimental results imply that optoelectronic properties of mesogenic materials could be affected not only by the molecular ordering but also by the enhancement of the electrical contact at interface between the ITO electrode and the LC layer through the course of the phase transitions. This photocurrent behavior for the binary mixture provided considerable potentials useful for photoconductive switches under the short-circuit condition. This binary mixture gives a new insight into understanding the processes of the photoinduced charge carrier generation and transport under short-circuit condition through the variation of the orientational order of molecules in each phase.