G. Weiser
Aug 15, 1992
Citations
0
Influential Citations
4
Citations
Journal
Synthetic Metals
Abstract
Abstract Electroreflectance spectra of poly-1,6-di(n-carbazolyl)-2,4-hexadiyne (DCHD), poly-2,4-hexadiyne-1,6-diol-bis( p -toluenesulfonate) (PTS) and poly-2,4-hexadiyne-1,6-diol-bis( p -fluorobenzenesulfonate) (PFBS) are analysed as the quadratic Stark effect of excitons of large oscillator strength. Satisfactory agreement with the data is obtained for quasi one-dimensional Wannier excitons whose ground state stretches over four to five repeat units of the polymer. A large Stark effect results from coupling of the excitons to their continuum states over an energy separation of 0.5 eV. Mixing of the continuum states by the field (Franz-Keldysh effect) leads to a further signal at the edge of these states whose size depends strongly on the sample quality. It is proposed that the Stark effect is the mechanism leading to the large non-linear susceptibility of polydiacetylene crystals.