Exciton transport and electron mobility of organized aggregates of cationic dye thiocyanates

Abstract

Films of cationic dye thiocyanates adsorbed on copper based substrates form organized structures by a process of templated self-assembly. The growth process is initiated by strong S-bonding of thiocyanate ions to Cu sites, followed by repetitive and alternate bonding of dye cations and thiocyanate anions by electrostatic and dipolar forces. Rhodamine B thiocyanate and several other cationic dye thiocyanates solid films deposited this way exhibit J-aggregation behavior with large red-shifts in the absorption spectrum. Photoelectrochemical experiments with Rhodamine B thiocyanate deposited CuSCN cathodes indicated exciton diffusion lengths of order of 100 nm and space charge saturation current measurements suggested nearly three orders of magnitude enhancement of the electron mobility in the J-aggregated film. The photovoltaic properties of heterojunctions sandwiching J-aggregated dye films between n- and p-type semiconductor surfaces are investigated for potential application as solar cells and photon detectors.