Spin relaxation of triplet excitons in molecular crystals

Berk, N. F.; Rosenthal, Jenny E.; Yarmus, L.

doi:10.1103/physrevb.28.4963

Cited by 7 publications

(4 citation statements)

References 20 publications

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“…The disappearance of 5 TT features is associated with a loss of spin coherence and decrease in exciton density due to population decay and eventual hopping orthogonal to the fastest transport direction, leading to fewer opportunities to refuse and generate 5 TT. The different decay rates of the 5 TT peaks ( Table 2 ) suggest that the equilibrium decay may also be faster at intermediate orientations ( 47 , 48 ). We also note that the degree of broadening exhibits some orientation dependence ( Fig.…”

Section: Discussionmentioning

confidence: 99%

Triplet-pair spin signatures from macroscopically aligned heteroacenes in an oriented single crystal

Rugg

Smyser

Fluegel

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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The photo-driven process of singlet fission generates coupled triplet pairs (TT) with fundamentally intriguing and potentially useful properties. The quintet 5 TT 0 sublevel is particularly interesting for quantum information because it is highly entangled, is addressable with microwave pulses, and could be detected using optical techniques. Previous theoretical work on a model Hamiltonian and nonadiabatic transition theory, called the JDE model, has determined that this sublevel can be selectively populated if certain conditions are met. Among the most challenging, the molecules within the dimer undergoing singlet fission must have their principal magnetic axes parallel to one another and to an applied Zeeman field. Here, we present time-resolved electron paramagnetic resonance (TR-EPR) spectroscopy of a single crystal sample of a tetracenethiophene compound featuring arrays of dimers aligned in this manner, which were mounted so that the orientation of the field relative to the molecular axes could be controlled. The observed spin sublevel populations in the paired TT and unpaired (T+T) triplets are consistent with predictions from the JDE model, including preferential 5 TT 0 formation at z ‖ B 0 , with one caveat—two 5 TT spin sublevels have little to no population. This may be due to crossings between the 5 TT and 3 TT manifolds in the field range investigated by TR-EPR, consistent with the intertriplet exchange energy determined by monitoring photoluminescence at varying magnetic fields.

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Section: Discussionmentioning

confidence: 99%

Triplet-pair spin signatures from macroscopically aligned heteroacenes in an oriented single crystal

Rugg

Smyser

Fluegel

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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“…This feature is ascribed to chromophore multiplication within dendrimer-like structures. Triplet hopping within dendrimer-like structures facilitates the spin relaxation process. , The spin relaxation process equally populates nine spin sublevels, encompassing 1 (TT), 3 (TT), and 5 (TT), as their energy spacings are markedly smaller than the thermal energy at room temperature . Consequently, in the absence of a spin-selective process capable of competing with the spin relaxation process, the MFE gradually vanishes over time, as evidenced in dendrimer-like structures.…”

Section: Resultsmentioning

confidence: 99%

“…The pronounced decays of fluorescence and TA signal within the first 20 ns are attributed to promoted S–Q transitions via all five active pathways of 1 (TT)↔ 5 (TT) under a magnetic field. However, in dendrimer-like structures, D-(Tc) 4 and D-(Tc) 6 , this initial MFE vanishes over time, due to the spin relaxation process via triplet hopping. , An intriguing observation is the facilitated multiexciton decorrelation in TriPh-L-(Tc) 2 under a magnetic field. A plausible interpretation of this finding is that 5 (TT) serves as an intermediate state for efficient multiexciton decorrelation .…”

Section: Resultsmentioning

confidence: 99%

“…However, in dendrimerlike structures, D-(Tc) 4 and D-(Tc) 6 , this initial MFE vanishes over time, due to the spin relaxation process via triplet hopping. 90,91 An intriguing observation is the facilitated multiexciton decorrelation in TriPh-L-(Tc) 2 under a magnetic field. A plausible interpretation of this finding is that 5 (TT) serves as an intermediate state for efficient multiexciton decorrelation.…”

Section: Journal Of the American Chemical Societymentioning

confidence: 99%

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Elucidating Singlet-Fission-Born Multiexciton Dynamics via Molecular Engineering: A Dilution Principle Extended to Quintet Triplet Pair

Kim,

Teo,

Hong

et al. 2024

J. Am. Chem. Soc.

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Multiexciton in singlet exciton fission represents a critical quantum state with significant implications for both solar cell applications and quantum information science. Two distinct fields of interest explore contrasting phenomena associated with the geminate triplet pair: one focusing on the persistence of long-lived correlation and the other emphasizing efficient decorrelation. Despite the pivotal nature of multiexciton processes, a comprehensive understanding of their dependence on the structural and spin properties of materials is currently lacking in experimental realizations. To address this gap in knowledge, molecular engineering was employed to modify the TIPStetracene structures, enabling an investigation of the structure− property relationships in spin-related multiexciton processes. In lieu of the time-resolved electron paramagnetic resonance technique, two time-resolved magneto-optical spectroscopies were implemented for quantitative analysis of spin-dependent multiexciton dynamics. The utilization of absorption and fluorescence signals as complementary optical readouts, in the presence of a magnetic field, provided crucial insights into geminate triplet pair dynamics. These insights encompassed the duration of multiexciton correlation and the involvement of the spin state in multiexciton decorrelation. Furthermore, simulations based on our kinetic models suggested a role for quintet dilution in multiexciton dynamics, surpassing the singlet dilution principle established by the Merrifield model. The integration of intricate model structures and timeresolved magneto-optical spectroscopies served to explicitly elucidate the interplay between structural and spin properties in multiexciton processes. This comprehensive approach not only contributes to the fundamental understanding of these processes but also aligns with and reinforces previous experimental studies of solid states and theoretical assessments.

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Triplet Excitation Transfer Studies in Organic Condensed Matter via Cooperative Effects

Ern¹

1984

NATO ASI Series

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Spin relaxation of triplet excitons in molecular crystals

Cited by 7 publications

References 20 publications

Triplet-pair spin signatures from macroscopically aligned heteroacenes in an oriented single crystal

Triplet-pair spin signatures from macroscopically aligned heteroacenes in an oriented single crystal

Elucidating Singlet-Fission-Born Multiexciton Dynamics via Molecular Engineering: A Dilution Principle Extended to Quintet Triplet Pair

Triplet Excitation Transfer Studies in Organic Condensed Matter via Cooperative Effects

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