Photoinduced voltage-decay characteristics of dye-sensitized poly-N-vinylcarbazole

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Abstract
Measurements of the photoinduced voltage‐decay of dye‐sensitized polyvinylcarbazole (PVK) films are reported. A reaction product of a benzopyrylium salt and a benzopyrane is, as the sensitizing dye, uniformly dispersed in the PVK films. The voltage‐decay characteristics are analyzed on the basis of a model assuming that holes are generated by an electron transfer from PVK to photoexcited dyes. The model is confirmed by this analysis and by comparing the voltage‐decay rate of the uniformly sensitized films with that of a double‐layer film consisting of an undoped PVK layer and a very thin dye‐sensitized PVK layer. The quantum efficiency of photogeneration of holes is found to increase linearly with the electric field and is estimated to be 0.52 at 106 V/cm. The mean range of holes at 106 V/cm is longer than 11 μ for the films containing less than 1.6 weight parts of the dye relative to 100 weight parts of PVK. The range decreases with the increase in the dye concentration.