CT-excitons and magnetic field effect in polydiacetylene crystals

Abstract A new method aimed at the estimation of an electron-hole exchange interaction distance in organic and possibly other semi-conductors is developed. It is based on studying the temperature dependence of the spin magnetic field effect on the photoconductivity. Photoexcitation of the polydiacetylene single crystal which is a quasi-dimensional semiconductor is shown to result in an appearance of delocalized on 70 A intermolecular charge transfer states the latter being precursors of free charge carriers. The energy of the CT states is estimated to be 0.12 eV below a conduction band. Spin evolution in the correlated electron-hole pair is shown to proceed when the e–h distance is up to 1600 A.