NATURE OF THE PRIMARY PHOTOEXCITATIONS IN POLY(ARYLENE-VINYLENES)

We present an overview of the optical properties and related experimen tal results obtained from poly(para-phenylene vinylene), PPV, and its soluble derivatives, and we critically examine the interpretation of t hese data in the context of both the band model and the exciton model of the electronic structure of these semiconducting and luminescent po lymers. Results obtained from highly oriented and structurally ordered PPVs demonstrate that the observed disparities between the physical p roperties of PPV and the polydiacetylenes (PDAs) are not due to disord er; these differences are intrinsic and arise from the fundamental dif ference in the nature of the low energy photoexcited states: excitons in the PDAs and free carriers in the PPVs.