Organometallic films on metal electrodes

The formation of photoactive films on metal electrodes is not restricted to inorganic materials. Copper, for example, can be anodised to form polymeric phenylacetylide [33] and acetylide [34] layers that appear to behave as p-type organic semiconductors. The photoconducting properties of the arylethynyl polymers have been known for some time, although the mechanism of photoconductivity is not well understood. It seems probable that charge carriers are created by the annihilation of mobile Frenkel excitons at electron traps such as adsorbed oxygen rather than by direct interband excitation. 

The existence of exciton states in polymers such as CuPA has not been considered in detail in the literature, but it seems reasonable to suppose that efficient energy transfer can occur along the polymer chains. The absorption transition has been attributed to the formation of a charge transfer state and it is therefore possible that exciton dissociation is enhanced by the local electric field. Alternatively, exciton dissociation may occur at the polymer surface, with the electron being transferred to an acceptor such as molecular oxygen. The reaction scheme 

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