Nature of the primary photoexcitations in poly(arylene-vinylenes)

We present an overview of the optical properties and related experimental results obtained from poly(para-phenylene vinylene), PPV, and its soluble derivatives, and we critically examine the interpretation of these data in the context of both the band model and the exciton model of the electronic structure of these semiconducting and luminescent polymers. Results obtained from highly oriented and structurally ordered PPVs demonstrate hat the observed isparities between the physical properties of PPV and the polydiacetylenes (PDAs) are not due to disorder; these differences are intrinsic and arise from the fundamental difference in the nature of the low energy photoexcited states: excitons in the PDAs and free carriers in the PPVs. I