Charge Carrier Photogeneration in Poly(phenylacetylene)

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Abstract
Pulsed photoconduction in poly(phenylacetylene) (PPA) has been studied between 220–700 nm. The photoconduction threshold has been detected at 410 nm, although the film absorption extends up to 550 nm. The action spectrum of the photocarrier generation efficiency shows a steep rise in the range 300–400 nm and a beginning of a plateau at shorter wavelengths. It is suggested that the mechanism of photogeneration is intrinsic by nature. The thermal activation of photogeneration suggests that the experimental results can be described within the framework of the ballistic model. The dissociation of electron-hole pairs is in a good agreement with predictions based on the Onsager theory of geminate recombination. From the temperature dependence as well as from the field dependence of the quantum yield, the pair separation distance was obtained as ca 2.2 nm. The fraction of absorbed photons which produce thermalized electron-hole pairs is close to 2 × 10−2 charges per photon.