Emission processes in conjugated polymer solutions and thin films

We report a study of the emissive properties of both solutions and thin films of a substituted polyfluorene. Our work, motivated by the observation of emission line narrowing phenomena in conjugated polymer thin films, shows that in solution the polymer acts largely as expected for an organic laser dye. From our results for films and from extrapolations as a function of increasing chromophore concentration in solution we rule out lasing as an explanation of the line narrowing. The possible roles played by superradiant and superfluorescent cooperative emission and by amplified spontaneous emission are discussed.