Effect of dye concentration in Langmuir multilayer photoconductors

Abstract The behaviour of anisotropic photoconductivities is studied in Langmuir films of rhodanine containing merocyanines with three different donor nuclei (benzoxazole (DO), benzothiazole (DS) and benzoselenazole (DSe) diluted with arachidic acid. DS and DSe films, which possess a J-like aggregate, share a common feature in the spectral shape of their photoconductivities; the J-like band is effective only in Δσ‖ and only at higher concentrations. The spectral shape for DO remains invariant for different concentrations. The magnitude of Δσ‖ distinguishes DSe from the others; Δσ‖ for DSe increases monotonically with concentration up to values a decade or more greater than those for DO and DS, which tend to saturate towards higher concentrations. The greater Δσ‖ for DSe disappears after heat treatment, as does the J-like band. These results suggest the important role of molecular coordination in the photoconduction process.