Multiexciton state of singlet fission in triisopropylsilylethynyl‐pentacene

Abstract

Singlet fission (SF) is a spin-allowed conversion process, in which one singlet exciton is replaced by a pair of triplet excitons resided on adjacent molecules. To rationalize this phenomenon, a multiexcitonic spin-zero triplet-pair state is generally hypothesized as an intermediate state for SF. However, the details of its formation during the fission process, and its subsequent evolution over time are still remain unclear. Thus, this work provides a model of the SF system for triisopropylsilylethynyl-pentacene by using femtosecond time-resolved transient absorption spectroscopy. A mixed state of singlet and multiexciton, which mediates the ultrafast SF process is directly observed. This work represents a new viewpoint for the research on SF intermediates.

Research Progress on Singlet Fission in Acenes and Their Derivatives

“…The S 1 and ME excitons undergo the decoupling of ME from S 1 , and evolve into the state of ME' state over the course of ~200 fs. Subsequently, the ME' state decays to the T 1 state with a time constant of ~1.5 ps [76]. Herz added sp 2 nitrogen atoms to the backbone of TIPS-pentacene, which led to the evolution of S 1 and ME to ME' state over the course of 110 fs and doubled the rate of the SF process (Figure 4).…”