DYE SENSITIZATION WITH OCTASUBSTITUTED LIQUID-CRYSTALLINE PHTHALOCYANINES

New liquid crystalline octaamide (C-12) and octaester (C-12) copper ph thalocyanines (LC-Pc), which form self-assembled structures in solutio ns and in cast films, act as effective sensitizers for the photoelectr ochemical response of the layered semiconductors, n-SnS2. The photocur rent yield spectra of these cast films, at a wide range of coverages, show a single sharp Q-band at a position corresponding to close packed monolayer assemblies of flat-lying Pc's. Quantum yields per absorbed photon are high (QYAP almost-equal-to 44%) for the close packed monola yers. In contrast, films from a short-chain substituted and an unsubst ituted CuPc on SnS2 show Q-band photocurrent yield spectra due to both the monomer and H-aggregate forms. These phenomena suggest that the e fficiency of exciton transport through a self-assembled LC-Pc film str ongly depends on the separation distance between the chromophores. The interfacial structure of the mesogenic molecules at the semiconductor or metal surface appears to be critical in determining the overall ex citon transport efficiency in columnar mesophases.