Oxygen-catalysed sequential singlet fission

Wollscheid, Nikolaus; Lustres, J. Luis Pérez; Kefer, Oskar; Hahn, Sebastian; Brosius, Victor; Bunz, Uwe H. F.; Motzkus, Marcus; Buckup, Tiago

doi:10.1038/s41467-019-13202-5

Cited by 21 publications

(28 citation statements)

References 31 publications

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“…As the TA experiments conducted here were undertaken under standard atmospheric conditions, it is also possible that dissolved oxygen may contribute to exciton quenching at the NP surface. However, previous studies of acene quenching by triplet oxygen have measured rate coefficients on the order of 10 9 to 10 10 s –1 , which is 1–2 orders of magnitude lower than the picosecond-scale S 1 deactivation observed here. , Therefore, singlet quenching by triplet oxygen is also unlikely to be the main cause of the non-radiative singlet decay observed here. Picosecond-scale non-radiative singlet decay in aqueously dispersed fullerene NPs has previously been attributed to exciton quenching by water .…”

Section: Resultscontrasting

confidence: 72%

Nanoparticle Size-Dependent Singlet Fission and Exciton Dynamics in Amorphous TIPS-Pentacene

et al. 2021

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Aqueous nanoparticle (NP) dispersions are commonly used as model systems for the spectroscopic study of singlet exciton fission (SF) in acenes such as 6,13-(triisopropylsilylethynyl)pentacene (TIPS-Pn). However, the potential for particle size effects to complicate interpretation of results in such model systems is generally ignored. In this work, we study amorphous TIPS-Pn NP dispersions prepared by the re-precipitation method over a range of particle sizes. Time-resolved fluorescence and femtosecond transient absorption spectroscopies show that exciton dynamics in these systems depend significantly upon particle size. Kinetic analysis reveals that SF becomes slower at smaller NP sizes, while triplet exciton decay (through both correlated triplet pair relaxation and geminate triplet–triplet annihilation) accelerates. These significant size-dependent effects are ascribed to increased morphological disorder within smaller NPs, weakening the intermolecular couplings which control SF and triplet migration. A non-radiative singlet quenching channel separate from SF is also identified, which has not been previously reported for NPs of SF-capable chromophores. This non-radiative singlet decay becomes a significant relaxation pathway at small particle sizes, substantially reducing SF yields. Interestingly, exciton kinetics in the largest NPs considered here (81 nm diameter) approach those of bulk amorphous TIPS-Pn. This work demonstrates that particle size effects are significant for small NPs of SF chromophores and must be accounted for in order to accurately model bulk materials with such NP dispersions.

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Section: Resultscontrasting

confidence: 72%

Nanoparticle Size-Dependent Singlet Fission and Exciton Dynamics in Amorphous TIPS-Pentacene

et al. 2021

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“…However, previous studies of acene quenching by triplet oxygen have measured rate coefficients on the order of 10 9 -10 10 s −1 , which is 1-2 orders of magnitude lower than the picosecond-scale S 1 deactivation observed here. 49,50 Therefore, singlet quenching by triplet oxygen is also unlikely to be the main cause of the non-radiative singlet decay observed here. Picosecond-scale non-radiative singlet decay in aqueously-dispersed fullerene NPs has previously been attributed to exciton quenching by water.…”

Section: Singlet Exciton Quenchingmentioning

confidence: 75%

Nanoparticle–Size–Dependent Singlet Fission and Exciton Dynamics in Amorphous TIPS-Pentacene

Hudson

Stuart

Perrelle

et al. 2021

Preprint

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Aqueous nanoparticle (NP) dispersions are commonly used as model systems for spectro- scopic study of singlet exciton fission (SF) in acenes such as 6,13-(triisopropylsilylethynyl) pentacene (TIPS-Pn). However, the potential for particle size effects to complicate interpretation of results in such model systems is generally ignored. In this work, we study amorphous TIPS-Pn NP dispersions prepared by the re-precipitation method over a range of particle sizes. Time-resolved fluorescence and femtosecond transient absorption spectroscopy show that exciton dynamics in these systems depend significantly upon particle size. Kinetic analysis reveals that SF becomes slower at smaller NP sizes, while triplet exciton decay (through both correlated triplet pair relaxation and geminate triplet-triplet annihilation) accelerates. These significant size-dependent effects are ascribed to increased morphological disorder within smaller NPs, weakening the intermolecular couplings which control SF and triplet migration. A non-radiative singlet quenching channel separate from SF is also identified, which has not been previously reported for NPs of SF-capable chromophores. This non-radiative singlet decay becomes a significant relaxation pathway at small particle sizes, substantially reducing SF yields. Interestingly, exciton kinetics in 81-nm NPs approach those of bulk amorphous TIPS-Pn, suggesting that NPs of this size or larger are likely good models for bulk TIPS-Pn. This work demonstrates that particle-size effects are significant for small NPs of SF chromophores, and must be accounted for in order to accurately model bulk materials with such NP dispersions.

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“…As the resulting estimation 80.7 × 10 6 s –1 is significantly lower than the observed values in all four molecules, this reaction channel is ruled out. The further possibility of a direct, diffusion-controlled SF process can be excluded due to the low concentration of the samples (≪0.1 mmol L –1 ). ,, Thus, it is concluded that the triplet state is formed via an ISC process with the rate constant k 2 . This is supported by the systematically increasing rates with substituent size for the three halogenated TAPPs and the concomitant decrease of the fluorescence quantum yield .…”

Section: Discussionmentioning

confidence: 99%

“…The formation of a triplet state in solution can in principle occur via ISC or, due to the high S 1 –T 1 energy gap (Table ), energy transfer to 3 O 2 . For the latter, an upper limit can be calculated using the quenching rate of oxygen and its concentration in acetonitrile .…”

Section: Discussionmentioning

confidence: 99%

Ultrafast Singlet Fission and Intersystem Crossing in Halogenated Tetraazaperopyrenes

et al. 2020

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Charge carrier multiplication via singlet fission into two triplet states has the potential to increase efficiencies of photovoltaics by one-third due to the reduction of thermalization losses. In the present work, we investigate tetraazaperopyrenes, a class of N-heteropolycyles, as suitable singlet fission candidates. Using a combined experimental and theoretical approach, fundamentally different mechanisms for triplet formation in solution and thin film are identified. In solution, an ultrafast intersystem crossing process is observed, which is accelerated for heavier halide substituents not only due to enhanced spin−orbit coupling but also due to the energy tuning between the S 1 and T 2 states. In thin films, a correlated triplet pair is formed coherently upon photoexcitation. Subsequently, an excimer formation is observed, which competes with the electronic decorrelation of the triplet pair. The comparison with peropyrene shows that aza-substitutions within the aromatic core can be a powerful strategy for tuning the energy levels of the states important to singlet fission.

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Oxygen-catalysed sequential singlet fission

Cited by 21 publications

References 31 publications

Nanoparticle Size-Dependent Singlet Fission and Exciton Dynamics in Amorphous TIPS-Pentacene

Nanoparticle Size-Dependent Singlet Fission and Exciton Dynamics in Amorphous TIPS-Pentacene

Nanoparticle–Size–Dependent Singlet Fission and Exciton Dynamics in Amorphous TIPS-Pentacene

Ultrafast Singlet Fission and Intersystem Crossing in Halogenated Tetraazaperopyrenes

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