Pitfalls of quantifying intersystem crossing rates in singlet-fission chromophore solutions

Author:

Stuart Alexandra N.1ORCID,Tapping Patrick C.1ORCID,Kee Tak W.1ORCID,Huang David M.1ORCID

Affiliation:

1. Department of Chemistry, The University of Adelaide, Adelaide, South Australia 5005, Australia

Abstract

Singlet fission (SF), a process that produces two triplet excitons from one singlet exciton, has attracted recent interest for its potential to circumvent the detailed-balance efficiency limit of single-junction solar cells. For the potential of SF to be fully realized, accurate assignment and quantification of SF is necessary. Intersystem crossing (ISC) is another process of singlet to triplet conversion that is important to distinguish from SF to avoid either over- or under-estimation of SF triplet production. Here, we quantify an upper bound on the rate of ISC in two commonly studied SF chromophores, TIPS–pentacene and TIPS–tetracene, by using transient absorption spectroscopy of solutions of varying concentrations in toluene. We show that SF in solutions of these acenes has previously been misidentified as ISC, and vice versa. By determining a bimolecular SF rate constant in concentrated solutions in which SF dominates over ISC, we distinguish triplet formation due to SF from triplet formation due to ISC and show that the characteristic time scale of ISC must be longer than 325 ns in TIPS–pentacene, while it must be longer than 118 ns in TIPS–tetracene. We additionally note that no excimer formation is observed in the relatively dilute (up to 8 mM) solutions studied here, indicating that previous excimer formation observed at much higher concentrations may be partially due to aggregate formation. This work highlights that an accurate quantification of ISC is crucial as it leads to accurate determination of SF rate constants and yields.

Funder

Australian Research Council

Publisher

AIP Publishing

Subject

Physical and Theoretical Chemistry,General Physics and Astronomy

Cited by 3 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

1. Role of Singlet and Triplet Excited States in the Oxygen-Mediated Photophysics and Photodegradation of Polyacenes;Journal of the American Chemical Society;2024-01-10

2. Photophysics in emerging photovoltaics;The Journal of Chemical Physics;2023-07-10

3. Singlet fission preserves polarisation correlation of excitons;Physical Chemistry Chemical Physics;2023

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