Reduced Photobleaching of Conjugated Polymer Films through Small Molecule Additives

Introduction. The photobleaching, or reduction in fluorescence quantum yield, of fluorescent dyes upon continuous excitation is a commonly encountered problem. The mechanism of photobleaching in fluorescent dyes has been shown to be complex, sensitive to environmental and excitation conditions, and specific to each dye. Nevertheless, two primary pathways are invoked to explain the photodegradation of fluorophores. In the first pathway, fluorophores are degraded by reaction with singlet oxygen, which is produced by sensitization of groundstate triplet oxygen by a small population of triplet-state fluorophores. The second pathway involves reactive radical intermediates formed by the photoionization of fluorophores upon excitation to the first or higher excited electronic states in a polar environment.