Dynamics of the triplet-pair state reveals the likely coexistence of coherent and incoherent singlet fission in crystalline hexacene

Nicholas R. Monahan, Dezheng Sun, Hiroyuki Tamura, Kristopher W. Williams, Bolei Xu, Yu Zhong, Bharat Kumar, Colin Nuckolls, Avetik R. Harutyunyan, Gugang Chen, Hai Lung Dai, David Beljonne, Yi Rao, X. Y. Zhu

    Research output: Contribution to journalArticlepeer-review

    104 Citations (Scopus)

    Abstract

    The absorption of a photon usually creates a singlet exciton (S1) in molecular systems, but in some cases S1 may split into two triplets (2×T1) in a process called singlet fission. Singlet fission is believed to proceed through the correlated triplet-pair 1(TT) state. Here, we probe the 1(TT) state in crystalline hexacene using time-resolved photoemission and transient absorption spectroscopies. We find a distinctive 1(TT) state, which decays to 2×T1 with a time constant of 270 fs. However, the decay of S1 and the formation of 1(TT) occur on different timescales of 180 fs and <50 fs, respectively. Theoretical analysis suggests that, in addition to an incoherent S11(TT) rate process responsible for the 180 fs timescale, S1 may couple coherently to a vibronically excited 1(TT) on ultrafast timescales (<50 fs). The coexistence of coherent and incoherent singlet fission may also reconcile different experimental observations in other acenes.

    Original languageEnglish
    Pages (from-to)341-346
    Number of pages6
    JournalNature Chemistry
    Volume9
    Issue number4
    DOIs
    Publication statusPublished - 2017 Apr 1

    ASJC Scopus subject areas

    • Chemistry(all)
    • Chemical Engineering(all)

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