Remarkable stability of the enhanced sharp photocurrent in methylviolet–C18 and rhodamine–C18 dye-sensitized photoelectrochemical cell with p-CuSCN

A remarkable stability in the sharp photo-current peak at 570 nm was found when p-CuSCN semiconductor photocathode was sensitized with double-dye LB films of rhodamine-C18 (R-C18) monolayers and methylviolet-C18 (M-C18) monolayers. At first, M-C18 four monolayers were deposited on p-CuSCN and then, R-C18 four monolayers were deposited on M-C18 monolayers to make an molecular arrangement on the semiconductor (LB-(R-C18(4)/M-C18(4))/p-CuSCN). Such a photo-cathode exhibited a remarkable stability of steady-state photo-current in (10−2 M) KI+(10−4 M) I2 aqueous solution of pH=6.5, where the quantum efficiency reached was 45%, as estimated by correcting the dye absorption in the sharp photo-current peak at 570 nm. When four monolayers of M-C18 and four monolayers of R-C18 were separated with an arachidic acid LB films, sharp photo-current peak and its stability gradually decreased. This remarkable stability may be due to an efficient energy transfer process and an efficient charge separation caused by a strong interaction between the parallel electron-vibration planes of both M-C18 and R-C18 molecules.