Electroabsorption Spectroscopy Of Poly(M-Phenylenevinylene-Co-2,5-Dioctoxy-P-Phenylenevinylene) And Related Materials

We report experimental studies of poly(m-phenylenevinylene-co-2,5-dioctoxy-p-phenylenevinylene) (PmPV-co-DOctOPV). Model oligomers based on this polymer have been synthesised and results on these materials are also presented. Electroabsorption measurements have been performed on spin coated films between 1.5 eV and 5 eV with electric fields of up to 200 KV/cm. Using Stark shift analysis the electroabsorption spectra are compared with the first derivative of the corresponding low temperature absorption spectra. We also investigate the effect of changes in chemical structure by studying the variation between the electroabsorption spectra of related materials. Samples of these polymers and oligomers that differ by the proportion of trans and cis vinylene bonds are also compared to see what effect the trans or cis bond has on the electronic structure. Increased cis content enhances emission efficiency but little alters the electroabsorption spectra. The results for the different materials are compared and several features occurring at the onset and at the minima of the electroabsorption spectra are considered. These features do not depend on the trans/cis ratio and we present evidence that suggests aggregation effects play an important role in these samples.