The effect of an electrostatic field on the photoluminescence and photoconductivity of polymer films doped by cationic polymethine dyes with end groups with different electron-donating properties

The effect of an external electrostatic field on the photoluminescence spectra and photoconductivity of symmetric and asymmetric cationic polymethine dyes with end groups possessing different electron-donating properties (basicity) in polymer films based on photoconductive poly-N-epoxypropylcarbazole and nonphotoconductive polyvinylethylal is studied. It is found that application of an electric field to films can both decrease and increase their luminescence intensity. The strongest decrease in the luminescence intensity is observed for symmetric dyes in poly-N-epoxypropylcarbazole films with either a decrease in the electron-donating ability of the end groups or with a decrease in the length of the polymethine chain. Colored polyvinylethylal films exhibit both a negative and a positive effect of the field on the photoluminescence intensity. The character of changes in the luminescence spectra does not depend on the electron-donating ability of the end groups. The spectral effects are explained by a change in the probability of vibronic transitions due to the redistribution of the electron density in the chromophore of the dye in the ground and excited states in an external electric field.