Spectroscopy of Conjugated Polymers: Phosphorescence and Delayed Fluorescence

摘要

We report on the observation of delayed fluorescence (DF) and phosphorescence (P) from films and dilute frozen solutions of various conjugated polymers of the PPP-type. The materials differ with respect to the rotational freedom along the polymer backbone. Upon pulsed optical excitation into the S_1←S_0 transition of the materials, delayed emission occurs on a time scale of μs to ms in solid films at 80 K. The phosphorescence in dilute frozen solution decays monoexponentially with a radiative lifetime on the order of one second. The data analysis reveals that the DF is caused by recombination of geminate electron hole pairs rather than triplet-triplet annihilation. This conclusion is supported by investigations of the response of the DF to an applied electric field.