Structural Disorder at the Edges of Rubrene Crystals Enhances Singlet Fission

Volek, Tanner S.; Armstrong, Zachary T.; Sowa, Jakub K.; Wilson, Kelly S.; Bohlmann Kunz, Miriam; Bera, Kajari; Koble, MaKenna; Frontiera, Renee R.; Rossky, Peter J.; Zanni, Martin T.; Roberts, Sean T.

doi:10.1021/acs.jpclett.3c02845

Cited by 5 publications

(6 citation statements)

References 60 publications

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“…In the two short-distance dimers (stacked and herringbone), the coupling of the localized S 1 with CT configurations is rather strong and in rather good agreement with previous calculations on the stacked dimer at the multireference second-order perturbation theory level (−175 and 86 meV, respectively), with the ZINDO approach (67 meV), and with evaluations of the HOMO–HOMO transfer integral (100–200 meV). ,,, In contrast, the 1 TT/AC and 1 TT/CA couplings vanish for the stacked and herringbone dimers. The effectively zero interaction between the spin-singlet triplet-pair configuration and CT states in the π-stacked dimer has been rationalized by orbital symmetry arguments. ,,, …”

Section: Computational Detailsmentioning

confidence: 99%

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Electronic Couplings for Triplet–Triplet Annihilation Upconversion in Crystal Rubrene

Diaz-Andres,

Tonnelé,

Casanova

2024

J. Chem. Theory Comput.

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Triplet–triplet annihilation photon upconversion (TTA-UC) is a process able to repackage two low-frequency photons into light of higher energy. This transformation is typically orchestrated by the electronic degrees of freedom within organic compounds possessing suitable singlet and triplet energies and electronic couplings. In this work, we propose a computational protocol for the assessment of electronic couplings crucial to TTA-UC in molecular materials and apply it to the study of crystal rubrene. Our methodology integrates sophisticated yet computationally affordable approaches to quantify couplings in singlet and triplet energy transfer, the binding of triplet pairs, and the fusion to the singlet exciton. Of particular significance is the role played by charge-transfer states along the b-axis of rubrene crystal, acting as both partial quenchers of singlet energy transfer and mediators of triplet fusion. Our calculations identify the π-stacking direction as holding notable triplet energy transfer couplings, consistent with the experimentally observed anisotropic exciton diffusion. Finally, we have characterized the impact of thermally induced structural distortions, revealing their key role in the viability of triplet fusion and singlet fission. We posit that our approaches are transferable to a broad spectrum of organic molecular materials, offering a feasible means to quantify electronic couplings.

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Section: Computational Detailsmentioning

confidence: 99%

“…The effectively zero interaction between the spin-singlet triplet-pair configuration and CT states in the π-stacked dimer has been rationalized by orbital symmetry arguments. 62 , 95 , 98 , 101 …”

Section: Computational Detailsmentioning

confidence: 99%

Electronic Couplings for Triplet–Triplet Annihilation Upconversion in Crystal Rubrene

Diaz-Andres,

Tonnelé,

Casanova

2024

J. Chem. Theory Comput.

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“…This averaging is often performed using a lock-in amplifier due to its ability to detect signals at frequencies that match the modulation rate of the pump pulse train. Indeed, TAM studies employing lock-in detection have provided key insights into carrier transport in 2D materials, ,− energy transport in quantum dots − and molecular assemblies, − and singlet fission dynamics in molecular crystals. − …”

Section: Introductionmentioning

confidence: 99%

Transient Absorption Microscopy Using Widefield Lock-in Camera Imaging

Wilson,

Volek,

Gross

et al. 2024

J. Phys. Chem. C

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Over the past decade, the proliferation of pulsed laser sources with high repetition rates has facilitated a merger of ultrafast time-resolved spectroscopy with imaging microscopy. In transient absorption microscopy (TAM), the excited-state dynamics of a system are tracked by measuring changes in the transmission of a focused probe pulse following photoexcitation of a sample. Typically, these experiments are done using a photodiode detector and lock-in amplifier synchronized with the laser and images highlighting spatial heterogeneity in the TAM signal are constructed by scanning the probe across a sample. Performing TAM by instead imaging a spatially defocused widefield probe with a multipixel camera could dramatically accelerate the acquisition of spatially resolved dynamics, yet approaches for such widefield imaging generally suffer from reduced signalto-noise due to an incompatibility of multipixel cameras with high-frequency lock-in detection. Herein, we describe implementation of a camera capable of high-frequency lock-in detection, thereby enabling widefield TAM imaging at rates matching those of high repetition rate lasers. Transient images using a widefield probe and two separate pump pulse configurations are highlighted. In the first, a widefield probe was used to image changes in the spatial distribution of photoexcited molecules prepared by a tightly focused pump pulse, while in the second, a widefield probe detected spatial variations in photoexcited dynamics within a heterogeneous organic crystal excited by a defocused pump pulse. These results highlight the ability of high-sensitivity lock-in detection to enable widefield TAM imaging, which can be leveraged to further our understanding of excited-state dynamics and excitation transport within spatially heterogeneous systems.

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“…Materials derived from the family of perylene-3,4,9,10-tetracarboxylic bisimide (perylene bisimide, PBI) are promising organic semiconductors, as they exhibit strong chemical, thermal, and photo stability , as well as high electron mobility and fluorescence quantum yields. , Self-assembly of the perylene core can produce structurally well-defined nanoscale objects. − If robustly translated to the solid state, such bottom-up design strategies could be leveraged to, for example, engineer materials with nonequilibrium structures aimed at specific functionalities. , Despite the promise, a robust and predictable approach for translating the well-defined structure of solvated self-assembled precursors into a solid-state material remains challenging …”

mentioning

confidence: 99%

“…Without high-resolution broadband , or multidimensional time-resolved microscopies, it is difficult to assign which specific mechanisms, for example, Frenkel–CT (charge transfer) exciton mixing, , excimer stabilization, and/or geometric rearrangement/self-trapping, are responsible for the longer lifetimes observed in the control film. However, since the films are chemically homogeneous, the variability in lifetime observed from site to site in the PBI-TEG film must reflect morphological defects and differences in intermolecular coupling.…”

mentioning

confidence: 99%

Covalently Tethered Assemblies Improve Energetic Homogeneity and Exciton Transport in Organic Materials

King,

Paulino,

Hollinbeck

et al. 2024

ACS Materials Lett.

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Structural and functional heterogeneity is a consequence of the weak noncovalent interactions that direct the formation of organic materials from solution precursors. While covalent tethering of solution-phase assemblies provides a compelling strategy to enhance intermolecular order, the effects of this tethering strategy on the formed solid-state materials remain unestablished. This work uses pump−probe microscopy to compare excited-state dynamics in thin films fabricated from tethered perylene bisimide assemblies to those fabricated from noncovalent assemblies. On average, tethered films exhibit faster and more homogeneous excited-state lifetimes, consistent with stronger and more uniform intermolecular coupling. Optical measurements of excited-state diffusion show that the tethered film has ∼75% faster transport than the control film. Kinetic Monte Carlo modeling suggests that the reduction of site energetic disorder is sufficient to quantitatively explain the difference in diffusion coefficients. These results provide strong support that covalent tethering is a promising strategy to enhance the structural and energetic ordering in molecular materials.

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Structural Disorder at the Edges of Rubrene Crystals Enhances Singlet Fission

Cited by 5 publications

References 60 publications

Electronic Couplings for Triplet–Triplet Annihilation Upconversion in Crystal Rubrene

Electronic Couplings for Triplet–Triplet Annihilation Upconversion in Crystal Rubrene

Transient Absorption Microscopy Using Widefield Lock-in Camera Imaging

Covalently Tethered Assemblies Improve Energetic Homogeneity and Exciton Transport in Organic Materials

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