Aggregated luminescence from light-emitting polymer in dilute solution

The photo-physical properties of a PPV derivative. Poly(dioctyloxy phenylene vinylene) (PdOPV) in various states good solvent, poor solvent and thin films were investigated. The solubility of PdOPV in toluene exhibits dramatic variation at different temperature. Below room temperature, the solubility is decreased, and polymer forms aggregates, even in dilute phase. This decreasing of solubility also introduces a quenching effect. From compared the absorption and fluorescence of the film and the poor solution, it was concluded that the films are comprised of individual polymer and interchain aggregates, but the fluorescence only exhibits the behavior of aggregates. In addition, at low temperature, the fluorescence dynamics of the films exhibits a wavelength dependent behavior, which excludes the vibronic origin for the feature of fluorescence. In the films, the aggregates suffer additional quenching, which reduces the fluorescence efficiency.