ELECTRICAL AND PHOTOELECTRICAL PROPERTIES OF COPPER TETRA[4-TERT-BUTYLPHTHALOCYANINE] LANGMUIR-BLODGETT-FILMS

The structure of Langmuir-Blodgett (LB) films prepared from copper tetra[4-t-butylphthalocyanine] (CuTTBPc) was studied using transmission electron microscopy, transmission electron diffraction and X-ray diffraction. Molecules in the LB film were stacked in layers with phthalocyanine rings tilted by 14-degrees to the substrate normal. Each molecular layer consisted of extended two-dimensional crystalline domains oriented anisotropically in the film plane. No relation between the anisotropic molecular orientation and in-plane electrical conductivity was observed. The in-plane electrical conductivity increased with time after voltage application reaching a stationary value 10(-1) S m-1. The Al/CuTTBPc LB film/Ni sandwich sample under illumination operated as a photovoltaic cell giving an open-circuit voltage of 0.4 V. The charge photogeneration quantum efficiency via excitation of the second single state of CuTTBPc was four times higher than that via excitation of the first singlet state. Possible photogeneration models are discussed.