Photoelectric Conversion with a Monolayer Incorporating a Cyanine Dye

Abstract

Photoelectric. conversion was studied with a mixed monolayer of arachic, acid and 3, 3'-dioctadecylthiacarbocyanine iodide in the. molar ratio 10: 1 on an Sb-doped SnO₂ semiconductor electrode prepared by the Langmuir-Blodgett technique. The absorption spectrum of the monolayer showed a, considerable dimerization of the dye in the monolayer, The appearance of the photocurrent action spectrum of the monolayer was very similar to that of the absorptio n spectrum. This indicates that both the photoexitation of the monomeric dye and that of the dimeric dye cause almost the same electron injection after all. However, this does not necessarily lead to the conclusion that the electron injection efficiency of the monomer and that of the dimer is nearly the same. The photocurrent must be given as a result of complicated processes which, involve, the two-dimensional energy transfer among the monomer and two types of dirpers. The intrinsic current, quantum, efficiency was measured for various electrode potential. It turned out that the onset potential of the, photocurrent was much positive (anodic) compared with the flat-band potential of the SnO₂ electrode. Some reasons for this finding are discussed.