Charge-Delocalized State and Coherent Vibrational Dynamics in Rigid PBI H-Aggregates

Kang, Seongsoo; Kim, Taeyeon; Hong, Yongseok; Würthner, Frank; Kim, Dongho

doi:10.1021/jacs.1c03276

Cited by 46 publications

(55 citation statements)

References 60 publications

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“…35). These results manifest the following hypotheses: (1) Since the xOOP mode plays a decisive role in the excimer formation 64,65 , the rise of xOOP mode shows the excimer-mediated MEG process by HP. (2) Considering the rate constants of MEG process depending upon the solvent-polarity, an absence of RB and RD modes in TOL suggests that these vibrational modes facilitate a mixing between the CT and LE/ME states.…”

Section: Insights Into Structural Dynamics For the Meg Process Throug...supporting

confidence: 54%

Steering the multiexciton generation in slip-stacked perylene dye array via exciton coupling

et al. 2022

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Dye arrays from dimers up to larger oligomers constitute the functional units of natural light harvesting systems as well as organic photonic and photovoltaic materials. Whilst in the past decades many photophysical studies were devoted to molecular dimers for deriving structure-property relationship to unravel the design principles for ideal optoelectronic materials, they fail to accomplish the subsequent processes of charge carrier generation or the detachment of two triplet species in singlet fission (SF). Here, we present a slip-stacked perylene bisimide trimer, which constitutes a bridge between hitherto studied dimer and solid-state materials, to investigate SF mechanisms. This work showcases multiple pathways towards the multiexciton state through direct or excimer-mediated mechanisms by depending upon interchromophoric interaction. These results suggest the comprehensive role of the exciton coupling, exciton delocalization, and excimer state to facilitate the SF process. In this regard, our observations expand the fundamental understanding the structure-property relationship in dye arrays.

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Section: Insights Into Structural Dynamics For the Meg Process Throug...supporting

confidence: 54%

Steering the multiexciton generation in slip-stacked perylene dye array via exciton coupling

et al. 2022

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“…A photoexcited rPBI-CP exhibits the broad ESA band covering 600–950 nm, which is characteristic of the excimer, as shown in Figure a . Especially, except for a minor increase at 610–640 nm (Figure b), the overall shape of ESA retains its spectral characteristics during excimer formation ( k = 200 fs –1 ). ,,,− By contrast, the TA spectra of gPBI-CP show a prominent increase with a time constant of ∼180 fs in the ESA band (∼825 nm), corresponding to the radical anionic band, in both TOL and BCN (Figures c,d and S27). However, the spectral shape in BCN is sharper compared with that in TOL.…”

Section: Resultsmentioning

confidence: 99%

Ultrafast Symmetry-Breaking Charge Separation in a Perylene Bisimide Dimer Enabled by Vibronic Coupling and Breakdown of Adiabaticity

et al. 2022

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Perylene bisimides (PBIs) have received great attention in their applicability to optoelectronics. Especially, symmetry-breaking charge separation (SB-CS) in PBIs has been investigated to mimic the efficient light capturing and charge generation in natural light-harvesting systems. However, unlike ultrafast CS dynamics in donor−acceptor heterojunction materials, ultrafast SB-CS in a stacked homodimer has still been challenging due to excimer formation in the absence of rigidifying surroundings such as a special pair in the natural systems. Herein, we present the detailed mechanism of ultrafast photoinduced SB-CS occurring in a 1,7-bis(N-pyrrolidinyl) PBI dimer within a cyclophane. Through narrow-band and broad-band transient absorption spectroscopy, we demonstrate that ultrafast SB-CS in the dimer is enabled by the combination of (1) vibrationally coherent charge-transfer resonance-enhanced excimer formation and (2) breakdown of adiabaticity (formation of SB-CS diabats) in the excimer state via structural and solvent fluctuation. Quantum chemical calculations also underpin that the participation of strong electrondonating substituents in overall vibrational modes plays a crucial role in triggering the ultrafast SB-CS. Therefore, our work provides an alternative route to facilitate ultrafast SB-CS in PBIs and thereby establishes a novel strategy for the design of optoelectronic materials.

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“…On the one hand, our group has very recently reported the characteristic intermolecular low‐frequency vibrations of the excimer state in cofacially stacked one‐dimensional perylene bisimide (PBI) H‐aggregates by using ultrafast time‐domain Raman spectroscopy. [33] We have suggested this low‐frequency interchromophore vibration presumably plays an important role in the excimer formation, however, have not analyzed the early‐time dynamics in detail. Therefore, it has remained still challenging to characterize full structural dynamics, which is of utmost importance to unveil how the excimer state is formed in the context of manipulating ultrafast photophysics of π‐stacked organic materials.…”

Section: Introductionmentioning

confidence: 99%

Real‐time Observation of Structural Dynamics Triggering Excimer Formation in a Perylene Bisimide Folda‐dimer by Ultrafast Time‐Domain Raman Spectroscopy

Hong

Kim

et al. 2022

Angew Chem Int Ed

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In π-conjugated organic photovoltaic materials, an excimer state has been generally regarded as a trap state which hinders efficient excitation energy transport. But despite wide investigations of the excimer for overcoming the undesirable energy loss, the understanding of the relationship between the structure of the excimer in stacked organic compounds and its properties remains elusive. Here, we present the landscape of structural dynamics from the excimer formation to its relaxation in a co-facially stacked archetypical perylene bisimide folda-dimer using ultrafast time-domain Raman spectroscopy. We directly captured vibrational snapshots illustrating the ultrafast structural evolution triggering the excimer formation along the interchromophore coordinate on the complex excited-state potential surfaces and following evolution into a relaxed excimer state. Not only does this work showcase the ultrafast structural dynamics necessary for the excimer formation and control of excimer characteristics but also provides important criteria for designing the π-conjugated organic molecules.

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Charge-Delocalized State and Coherent Vibrational Dynamics in Rigid PBI H-Aggregates

Cited by 46 publications

References 60 publications

Steering the multiexciton generation in slip-stacked perylene dye array via exciton coupling

Steering the multiexciton generation in slip-stacked perylene dye array via exciton coupling

Ultrafast Symmetry-Breaking Charge Separation in a Perylene Bisimide Dimer Enabled by Vibronic Coupling and Breakdown of Adiabaticity

Real‐time Observation of Structural Dynamics Triggering Excimer Formation in a Perylene Bisimide Folda‐dimer by Ultrafast Time‐Domain Raman Spectroscopy

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