Crystal violet dye-sensitized photocurrent by participation of surface states on p-CuSCN photocathode

Surface states on p-CuSCN are sensitized by aggregated crystal violet in ad dition to the cathodic sensitization process between semiconductor valence band and the excited monomeric dye molecules. Formation of surface states o n bare p-CuSCN is confirmed by experimental results of photocurrent measure ments, diffuse reflectance spectra and photoluminescence measurements. Phot ocurrent quantum efficiency obtained for the aggregated dyes sensitized the surface is 25% at lambda = 460 nm, and 14% for the monomeric dyes at lambd a = 580 nm. From the variation of photocurrent quantum efficiency with surf ace concentration of crystal violet at various biased electrode potentials and diffuse reflectance spectra of dye coated p-CuSCN; it is found that the appearance of the sharp photocurrent quantum efficiency peak (lambda = 460 nm) is due to the sensitization process with the aggregated dye and that o f the broad photocurrent quantum efficiency peak (lambda = 580 nm) is due t o the sensitization process with the monomeric dye. (C) 1999 Elsevier Scien ce B.V. All rights reserved.