Abstract
Control of interchain separation enables the optical properties of polymer thin films to be altered.
We present a thin film preparation technique that increases the free volume fraction in spin coated
polymer thin films resulting in reduced interchain interaction. The polaron yield, measured using
photoinduced absorption, was significantly reduced as a direct result of the increased interchain
separation, leading to a higher value for the measured photoluminescence efficiency. Impedance
spectroscopy showed an increase in permittivity, probably due to greater polarizability. Increases
approaching one order of magnitude were observed for direct current hole conductivity and mobility
values. Space charge limited conduction analysis suggests a narrowing of the highest occupied
molecular orbital band tail on treatment resulting in reduced trapping. Single layer light emitting
devices prepared using this technique were found to be significantly brighter and to have longer
operating lifetimes.