Ultrafast electron injection from excited dye molecules into semiconductor electrodes

Abstract

Fluorescence decay of adsorbed dye molecules is measured on semiconductor electrodes where their stationary photoelectrochemical current approaches the yield of one electron per absorbed photon, also on solids where injection cannot occur and finally on a semiconductor where the current yield is low. At very low coverages, Θ·~10 −2, the fluorescence decay of an efficiently injecting ruthenium complex is faster than 10 ps on a polycrystalline TiO 2 electrode and also that of the efficiently injecting cresyl violet monomer on single crystal n-SnS 2. At higher coverage Θ⪰0,1, fluorescence decay is not only controlled by electron injection, exhibiting a very different dependence on dye coverage for different dye/semiconductor combinations with high injection yields at low coverages. Ultrafast and fast electron injection from vibronic excited dye monomers into the wide conduction band of semiconductors is discussed. The yield of stationary photoelectrochemical injection currents is discussed for different dye coverages taking into account the measured fluorescence decay behavior.