Singlet fission is a form of multiple exciton generation in which two triplet excitons are produced from the decay of a photoexcited singlet exciton. This process has only been observed in a few classes of organic materials to date, most notably the polyacenes. Of these materials, efficient singlet fission occurs only in the condensed phase, with the singlet fission rate and total yield being sensitive to both local and long-range order. A particular challenge is the identification of materials capable of an intramolecular fission process, where two triplets are produced on the same molecule and in which geometric order and strong nearest neighbor coupling is no longer a design constraint. However, a poorly understood mechanism for fission along with strict energy and geometry requirements have so far limited the development of isolated molecules capable of efficient intramolecular singlet fission. Here, we report “push-pull” type polymers and small molecules containing strong acceptor units that for the first time exhibit intramolecular fission yields in excess of 100%. We demonstrate how the triplet yield can be directly quantified as a function of energetic driving force and degree of charge transfer character of the singlet state. These results allow us to gain mechanistic insight into the fission process and suggest general strategies for generating new materials that can undergo efficient fission.

Efficient intramolecular singlet fission in organic molecules

249th National Meeting (2015)

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