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We discuss here our most recent results with the characterization of epitaxial deposits of various phthalolcyanine dyes formed by vacuum deposition (O/I-MBE) or solution deposition on the surface of metal dichalcogenide semiconductors, such as SnS2. Surface electron diffraction techniques used during the vacuum deposition process help to verify the type and extent of long range ordering of these dyes. SnS2 semiconductor substrates allow for the photoelectrochemical characterization of the dye layers, starting with the deposition of submonolayer amounts of material. High quantum yields per absorbed photon are seen for ultrathin films of InPc-Cl, VOPc, and CuPc on SnS2, and the photocurrent spectra suggest similar ordering at the monolayer level, even though multilayer structures are quite different. Ordered Pc thin films are also obtained for a new class of liquid crystalline phthalocyanines (LC-Pc), where the hydrocarbon side chains are attached to the Pc ring by amide linkages. Deposition of ultrathin films of these materials produces photocurrent spectra which are quite similar to those obtained for low coverages of the vacuum deposited Pc. Photocurrent spectra on SnS2 show that the first monolayer of material may have a completely different surface structure than the bulk of the multilayer LC-Pc thin film. The nature of dye/dye' interfaces and their effect on exciton dissociation events has also been explored using vacuum deposited materials. Superlattices of Pcs were formed by vacuum deposition, where the active dye was sandwiched between various spacer molecules with thicknesses down to a few molecular layers. Transient photocurrent yield spectra from such assemblies suggests that exciton dissociation events in such materials can be confined to within a few molecular layers of the dye/dye' interface.
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