Optimizing through-space interaction for singlet fission by using macrocyclic structures

Wang, Zhangxia; Yang, Xue-Xiao; Ma, Hao; Xie, Xiaoyu

doi:10.1039/d3tc01077e

Cited by 2 publications

(5 citation statements)

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“…In recent years, particularly in macrosystems like oligomers and polymers, a flexible structure with dynamic conformations appears to reduce recombination from 1 (TT) and enhance long-lived triplet formation. – This has emerged as a potential design tool to complement the control of the linker’s electronic nature. However, despite a few studies that probe the effects of well-defined through-space couplings, – , the field lacks a systematic view of how specific conformations impact the iSF dynamics.…”

Section: Introductionmentioning

confidence: 99%

Controlling Intramolecular Singlet Fission Dynamics via Torsional Modulation of Through-Bond versus Through-Space Couplings

Majumder,

Mukherjee,

Panjwani

et al. 2023

J. Am. Chem. Soc.

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Covalent dimers, particularly pentacenes, are the dominant platform for developing a mechanistic understanding of intramolecular singlet fission (iSF). Numerous studies have demonstrated that a photoexcited singlet state in these structures can rapidly and efficiently undergo exciton multiplication to form a correlated pair of triplets within a single molecule, with potential applications from photovoltaics to quantum information science. One of the most significant barriers limiting such dimers is the fast recombination of the triplet pair, which prevents spatial separation and the formation of long-lived triplet states. There is an ever-growing need to develop general synthetic strategies to control the evolution of triplets following iSF and enhance their lifetime. Here, we rationally tune the dihedral angle and interchromophore separation between pairs of pentacenes in a systematic series of bridging units to facilitate triplet separation. Through a combination of transient optical and spin-resonance techniques, we demonstrate that torsion within the linker provides a simple synthetic handle to tune the fine balance between through-bond and through-space interchromophore couplings that steer iSF. We show that the full iSF pathway from femtosecond to microsecond timescales is tuned through the static coupling set by molecular design and structural fluctuations that can be biased through steric control. Our approach highlights a straightforward design principle to generate paramagnetic spin pair states with higher yields.

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Section: Introductionmentioning

confidence: 99%

Controlling Intramolecular Singlet Fission Dynamics via Torsional Modulation of Through-Bond versus Through-Space Couplings

Majumder,

Mukherjee,

Panjwani

et al. 2023

J. Am. Chem. Soc.

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“…In our previous work, we maintained the π–π packing between two pentacenes and optimized the through-space interaction of iSF in bipentacene macrocycles (BPcs) . We aim to take advantage of the molecular control inherent in intramolecular singlet fission (iSF) to help with the challenging control of packing in intermolecular singlet fission (xSF).…”

mentioning

confidence: 99%

“…In this work, we evaluated the rates of iSF and xSF following our previous work. Previously, we explained that the SF rate of BPc in a dilute solution mainly depends on the distance between two pentacenes and is weakly affected by the type of organic macrocycle . To examine the SF behavior of thin films or intermediate products in the evaporation process, one only needs to consider the relative positions between two pentacenes.…”

mentioning

confidence: 99%

“…In our previous work, we maintained the π−π packing between two pentacenes and optimized the through-space interaction of iSF in bipentacene macrocycles (BPcs). 39 We aim to take advantage of the molecular control inherent in intramolecular singlet fission (iSF) to help with the challenging control of packing in intermolecular singlet fission (xSF). Adjusting the solid-state electronic properties of monomers is experimentally challenging, as the chromophore interactions are highly sensitive to slight changes in the chromophore arrangement.…”

mentioning

confidence: 99%

“…Previously, we explained that the SF rate of BPc in a dilute solution mainly depends on the distance between two pentacenes and is weakly affected by the type of organic macrocycle. 39 To examine the SF behavior of thin films or intermediate products in the evaporation process, one only needs to consider the relative positions between two pentacenes. The affected parameters include the slipped distance in three directions in 3D space and the angle between molecules.…”

mentioning

confidence: 99%

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Simultaneous Intra- and Intermolecular Singlet Fission in Bipentacene Macrocycle Aggregates

Wang,

Xie,

2024

J. Phys. Chem. Lett.

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Singlet fission (SF) is a process where a singlet state splits into two triplet states, which is essential for enhancing optoelectronic devices. Macrocyclic structures allow for precise control of chromophore orientation and facilitate singlet fission in solutions. However, the behavior of these structures in thin films, crucial for solid-state device optimization, remains underexplored. This study examines the aggregation and singlet fission processes of bipentacene macrocycles (BPc) in thin films using molecular dynamics simulations and electronic structure calculations. Findings indicate that BPc aggregates more rapidly with less chloroform, aligning parallel to the substrate. Intramolecular singlet fission (iSF) rates are rarely changed during evaporation, but the efficiency of intermolecular singlet fission (xSF) improves due to the increase in packing domains, suggesting that orderly crystal domains are not necessary for device efficiency. This opens avenues for varied device designs and traditional solution-based methods for optimal device development.S inglet fission (SF), a phenomenon observed in organic compounds, involves a high-energy singlet-state chromophore transferring excitation energy to an adjacent chromophore, forming two lower-energy triplet states. This mechanism, distinct from those in traditional semiconductors, allows SF materials to generate two electron−hole pairs for every photon absorbed, potentially doubling photocurrent efficiency. 1−3 Recent studies have shown that SF occurs within femtosecond time scales and achieves up to 200% triplet yields in materials like pentacene and its derivatives. 4−7 For SF to occur efficiently, the chromophores should meet two energetic requirements (E(S 1 ) ≥ 2E(T 1 ) and E(T 2 ) ≥ 2E(T 1 )) and possess adequate coupling via interchromophoric interactions. 8 Generally, electronic coupling comes from either intermolecular through-space or intramolecular through-bond interactions, usually corresponding to intermolecular singlet fission (xSF) and covalent-bonded intramolecular singlet fission (iSF), respectively. 9−11 In the scenario of through-space interaction, the spatial orbital overlap between two chromophores is facilitated by their specific tight packing arrangement. Conversely, in through-bond interactions, the orbital of the linker exhibits strong coupling with the two chromophores within the same molecule, thereby amplifying their effective interaction. The through-space mechanism depends on molecular aggregation and predominantly takes place in structures like crystals, 12−14 films, 15−19 nanoparticles, 20 or solutions with high concentration, 21,22 while the through-bond interaction can also be observed in dilute solutions. 4,5,23−25 Recently, researchers developed a new design concept for

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Optimizing through-space interaction for singlet fission by using macrocyclic structures

Abstract: There is great interest in the exploitation of singlet fission (SF) materials to improve the power con version efficiency (PCE) of solar cells. Usually ultrafast SF is achieved as an...

Cited by 2 publications

References 114 publications

Controlling Intramolecular Singlet Fission Dynamics via Torsional Modulation of Through-Bond versus Through-Space Couplings

Controlling Intramolecular Singlet Fission Dynamics via Torsional Modulation of Through-Bond versus Through-Space Couplings

Simultaneous Intra- and Intermolecular Singlet Fission in Bipentacene Macrocycle Aggregates

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