Singlet Fission is an ultrafast spin-allowed exciton multiplication process in which singlet excitons are converted into two triplets. Despite a great deal of attention, it remains a challenge to directly characterize the dynamic intermediates that lead to singlet fission. Using ultrafast infrared spectroscopy from the femtosecond to millisecond time scales, we demonstrate that correlated triplet pair states in a solution processed pentacene derivative exhibit weak electronic transitions in the mid-infrared superimposed on their native vibrational features. Analyzing the dynamics of both the electronic and vibrational features reveals that the formation of independent triplet excitons involves numerous dissociation and reformation events and that the formation of independent triplets occurs over a time scale two orders of magnitude longer than previously recognized.  Our findings reveal that understanding the dynamics leading to final triplet state dissociation may be essential for designing systems that efficiently harvest multiplied triplet excitons in practical applications.

Dynamic intermediates in singlet fission observed with ultrafast infrared spectroscopy

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.