The role of conformational heterogeneity in the excited state dynamics of linked diketopyrrolopyrrole dimers

Bradley, Siobhan J.; Ming, Chi; White, Jonathan M.; Goerigk, Lars; Smith, Trevor A.; Ghiggino, Kenneth P.

doi:10.1039/d1cp00541c

Cited by 16 publications

(22 citation statements)

References 42 publications

(51 reference statements)

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“…It is likely that similar to the case of the acenes 19 , 74 – 82 , experiments on tailored dimers in solution (where thermal effects are negligible due to rapid heat dissipation) could provide a detailed mechanistic insight into the SF pathway in DPPs. To date, though, such structures have tended to exhibit only symmetry-breaking charge transfer or SO-ISC, without any 1 (TT) formation 83 , 84 .…”

Section: Discussionmentioning

confidence: 99%

Parallel triplet formation pathways in a singlet fission material

et al. 2022

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Harvesting long-lived free triplets in high yields by utilizing organic singlet fission materials can be the cornerstone for increasing photovoltaic efficiencies potentially. However, except for polyacenes, which are the most studied systems in the singlet fission field, spin-entangled correlated triplet pairs and free triplets born through singlet fission are relatively poorly characterized. By utilizing transient absorption and photoluminescence spectroscopy in supramolecular aggregate thin films consisting of Hamilton-receptor-substituted diketopyrrolopyrrole derivatives, we show that photoexcitation gives rise to the formation of spin-0 correlated triplet pair 1(TT) from the lower Frenkel exciton state. The existence of 1(TT) is proved through faint Herzberg-Teller emission that is enabled by vibronic coupling and correlated with an artifact-free triplet-state photoinduced absorption in the near-infrared. Surprisingly, transient electron paramagnetic resonance reveals that long-lived triplets are produced through classical intersystem crossing instead of 1(TT) dissociation, with the two pathways in competition. Moreover, comparison of the triplet-formation dynamics in J-like and H-like thin films with the same energetics reveals that spin-orbit coupling mediated intersystem crossing persists in both. However, 1(TT) only forms in the J-like film, pinpointing the huge impact of intermolecular coupling geometry on singlet fission dynamics.

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Section: Discussionmentioning

confidence: 99%

Parallel triplet formation pathways in a singlet fission material

et al. 2022

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“…CycloHexane is used for the polyacenes due to its weak dispersive interaction with aromatic molecules, especially since the larger polyacenes have some solubility issues 14 . DiMethyl Sulfoxide is used for DPP, as it is solvatochromic in nature 51 , and therefore requires a highly polar solvent, while Toluene is used for PDI, as it is non-polar and also minimised interchromophore coupling in experimental solution 52 .…”

Section: B Quantum Chemistrymentioning

confidence: 99%

“…As shown in recent studies 44,46,51,86 , the photophysical properties of DPP are incredibly sensitive to the sidegroups attached to the chomophore, in some cases, stabilising in energy by more than 1.0 eV. Since DPP has only recently come into light as an interesting compound for application of fluorescence technologies, comparison of the core chromophore with studies in the literature is difficult, as the physics revolves around it's derivatives.…”

Section: A Quantum Chemical Analysismentioning

confidence: 99%

Modeling radiative and non-radiative pathways at both the Franck–Condon and Herzberg–Teller approximation level

Manian¹,

Shaw

Lyskov³

et al. 2021

The Journal of Chemical Physics

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Here, we present a concise model which can predict the photoluminescent properties of a given compound from first principles, both within and beyond the Franck-Condon approximation. The formalism required to compute fluorescence, Internal Conversion (IC), and Inter-System Crossing (ISC) is discussed. The IC mechanism in particular is a difficult pathway to compute due to difficulties associated with the computation of required bosonic configurations and non-adiabatic coupling elements. Here, we offer a discussion and breakdown on how to model these pathways at the Density Functional Theory (DFT) level, with respect to its computational implementation, strengths and current limitations. The model is then used to compute the photoluminescent quantum yield (PLQY) of a number of small but important compounds: Anthracene, Tetracene, Pentacene, diketo-pyrrolo-pyrrole (DPP), and Perylene Diimide (PDI), within a polarizable continuum model. Rate constants for fluorescence, IC, and ISC compare well for the most part with respect to experiment, despite triplet energies being overestimated to a degree. The resulting PLQYs are promising with respect to the level of theory being DFT. While we obtained a positive result for PDI within the Franck-Condon limit, the other systems require a second order correction. Recomputing quantum yields with Herzberg-Teller terms yields PLQYs of 0.19, 0.08, 0.04, 0.70, and 0.99 for Anthracene, Tetracene, Pentacene, DPP, and PDI respectively. Based on these results, we are confident the presented methodology is sound with respect to the level of quantum chemistry, and presents an important stepping stone in the search for a tool to predict properties of larger, coupled systems.

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“…8,12,21,22 Given the large size of these molecules, discussions about their electronic structure properties are often based on the density functional theory (DFT) HOMO-LUMO gaps or linear-response time-dependent DFT (TDDFT) excitations. 19,21,23,24 Nevertheless, depending on the molecular architecture, DFT and TDDFT cannot correctly describe DPPs derivatives, and characterizing these large molecules' lowlying doubly excited states is still a challenge for computational chemistry. We face this challenge, delivering a methodological road map for further studies.…”

Section: Introductionmentioning

confidence: 99%

Using diketopyrrolopyrroles to stabilize double excitation and control internal conversion

Casal

Toldo

Plasser

et al. 2022

Preprint

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Diketopyrrolopyrrole (DPP) is a pivotal functional group to tune the physicochemical properties of novel organic photoelectronic materials. Among its multiple uses, DPP-thiophene derivatives forming a dimer through a vinyl linker were recently shown to quench the fluorescence observed in their isolated monomers. Here, we explain this fluorescence quenching using computational chemistry. The DPP-thiophene dimer has a low-lying doubly excited state that is not energetically accessible for the monomer. This state delays the fluorescence allowing internal conversion to occur first. We characterize the doubly excited state wavefunction by systematically changing the derivatives to tune the pi-scaffold size and the acceptor and donor characters. The origin of this state's stabilization is related to the increase in the π-system and not to the charge-transfer features. This analysis delivers core conceptual information on the electronic properties of organic chromophores arranged symmetrically around a vinyl linker, opening new ways to control the balance between luminescence and internal conversion.

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The role of conformational heterogeneity in the excited state dynamics of linked diketopyrrolopyrrole dimers

Abstract: Diketopyrrolopyrrole (DPP) derivatives have been proposed for both singlet fission and energy upconversion as they meet the energetic requirements and exhibit superior photostability compared to many other chromophores. In this...

Cited by 16 publications

References 42 publications

Parallel triplet formation pathways in a singlet fission material

Parallel triplet formation pathways in a singlet fission material

Modeling radiative and non-radiative pathways at both the Franck–Condon and Herzberg–Teller approximation level

Using diketopyrrolopyrroles to stabilize double excitation and control internal conversion

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