Controlled Fluorescence Bursts from Conjugated Polymers Induced by Triplet Quenching

Dramatic fluorescence bursts (see Figure and cover) from conjugated polymers are observed upon exposure to air. The burst occurs prior to photo‐oxidation and is imaged in single molecules of a ladder‐type polymer, but is also found in bulk films. Triplet shelving is identified as an important mechanism limiting the fluorescence yield of conjugated polymers due to both a reduction in photon cycling rates and singlet–triplet quenching in the multichromophoric system.