Spectroscopic analysis of vibrational coupling in multi-molecular excited states

Hammer, Sebastian; Linderl, Theresa; Tvingstedt, Kristofer; Brütting, Wolfgang; Pflaum, Jens

doi:10.1039/d2mh00829g

Cited by 7 publications

(5 citation statements)

References 72 publications

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“…These observations can be naturally explained if the STE state in CANBIC perovskites is assumed to be of a highly localized character and behaving as an excited state in molecular assemblies, such as J-aggregates of dyes or organic excimers. [107,108] For such systems, a simple model of the totally accessible density of states (DOS) was proposed to interpret the temperature dependence of the spectral parameters of the fluorescence band (peak position, spectral width), [107] assuming the PL spectrum F(hv) to be a product of the low-temperature (T = 0) absorption spectrum A(hv) and an exponential function describing the thermal distribution of possible excitonic states, F(hv) = A(hv)×exp(À hv/k B T), where hv is the energy, k B is the Boltzmann constant.…”

Section: Discussion Of Ste Character Of Pl Emissionmentioning

confidence: 99%

Exploring Highly Efficient Broadband Self‐Trapped‐Exciton Luminophors: from 0D to 3D Materials

Stroyuk,

Raievska,

Zahn

et al. 2023

The Chemical Record

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The review summarizes our recent reports on brightly‐emitting materials with varied dimensionality (3D, 2D, 0D) synthesized using “green” chemistry and exhibiting highly efficient photoluminescence (PL) originating from self‐trapped exciton (STE) states. The discussion starts with 0D emitters, in particular, ternary indium‐based colloidal quantum dots, continues with 2D materials, focusing on single‐layer polyheptazine carbon nitride, and further evolves to 3D luminophores, the latter exemplified by lead‐free double halide perovskites. The review shows the broadband STE PL to be an inherent feature of many materials produced in mild conditions by “green” chemistry, outlining PL features general for these STE emitters and differences in their photophysical properties. The review is concluded with an outlook on the challenges in the field of STE PL emission and the most promising venues for future research.

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Section: Discussion Of Ste Character Of Pl Emissionmentioning

confidence: 99%

Exploring Highly Efficient Broadband Self‐Trapped‐Exciton Luminophors: from 0D to 3D Materials

Stroyuk,

Raievska,

Zahn

et al. 2023

The Chemical Record

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“…The coupling between Frenkel excitons and molecular vibrations, either intramolecular or intermolecular, is an enduring theme in the study of electronic excitations in organic molecular aggregates, crystals, and polymers, − as such coupling strongly impacts energy transport − ,,− ,− ,, as well as basic photophysical properties such as absorption and photoluminescence. − ,,,− Self-trapping of Frenkel excitons due to coupling between excitons and intermolecular vibrations (or lattice phonons) has been a subject of considerable interest since the pioneering works of Toyozawa, Rashba, , and Sumi , and has been implicated as the primary mechanism for the broad, red-shifted emission in some J-aggregate-forming dyes. − Strongly related to self-trapped excitons are excimers, where the latter are usually distinguished from the former by the involvement of charge-transfer (CT) states. − For both self-trapped excitons and excimers, photoluminescence is characterized by a red-shifted, featureless emission with a low quantum yield.…”

Section: Introductionmentioning

confidence: 99%

Impact of Local and Nonlocal Vibronic Coupling on the Absorption and Emission Spectra of J- and H-Dimers

Haghshenas,

Spano

2024

J. Chem. Theory Comput.

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The impact of exciton-vibrational (EV) coupling involving low-energy ("slow") intermolecular vibrations and higher-energy ("fast") intramolecular vibrations on the absorption and emission spectra of H-and J-dimers is studied theoretically for a pair of chromophores with excitonic coupling dominated by transition dipole−dipole coupling, J C . Exact quantum-mechanical solutions based on a Frenkel−Holstein−Peierls Hamiltonian reveal a fascinating interplay between the two coupling sources in determining the spectral line widths, Stoke shifts and radiative decay rates. It is shown that the ratio rules derived from the vibronic progression of the fast mode in molecular dimers remain valid under the influence of slow-mode EV coupling under most conditions. However, a highly unusual aggregate behavior occurs when the product of local and nonlocal couplings, |g L g NL |, exceeds 2ℏω s |J C |, where ℏω s is the energy of the slow mode. In this regime and when g L and g NL are in-phase, an H-dimer (J C > 0) becomes strongly emissive and can even be super-radiant, while a J-dimer (J C < 0) with out-of-phase g L and g NL values becomes subradiant. Such behaviors are in marked contrast to the predictions of Kasha theory and demonstrate the richness of the photophysical behavior resulting from EV coupling involving inter-and intramolecular vibrations.

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“…A rigorous procedure would involve calculation of vibrational broadening by evaluating Franck-Condon factors state. [52][53][54][55][56][57] More often, however, a simpler approach is employed in which only vertical transitions are considered and the stick spectra are broadened (using empirical parameters) to account for vibrational, inhomogeneous, and instrumental broadening. 58 This work is motivated by the results of our previous computational and experimental study on the exciplex formed between the excited-state oligo(p-phenylene) (OPP-n) acceptor and ground state triethylamine (TEA or Et 3 N) donor.…”

Section: Introductionmentioning

confidence: 99%

Simulating Excited-State Complex Ensembles: Fluorescence and Solvatochromism in Amine-Arene Exciplexes

Patra

Krylov

Sharada

2023

Preprint

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Exciplexes are excited-state complexes formed as a result of partial charge-transfer from the donor to the acceptor species. They are formed when one moiety of the donor-acceptor pair is electronically excited. The arene-amine exciplex formed between oligo-(p-phenylene) (OPP) and triethylamine (TEA) is of interest in photoredox catalysis for CO2 reduction as it can compete with complete quenching and electron transfer to OPP. Formation of the exciplex can therefore hinder the generation of a radical anion OPP·− necessary for subsequent CO2 reduction. We report an implementation of a workflow automating quantum-chemistry calculations that generate and characterize an ensemble of structures to represent this exciplex state. We use FireWorks, Pymatgen, and Custodian python packages for high-throughput ensemble generation via TDDFT optimization, verification of excited-state minima, and exciplex characterization with natural transition orbitals, exciton analysis, excited-state Mulliken charges, and energy decomposition analysis. Fluorescence spectra computed for these ensembles using Boltzmann-weighted contributions from each structure agree better with experiment than our previous work that employed a single representative exciplex structure (Kron, K. J. et al. J. Phys. Chem. A, 2022, 126, 2319–2329). The ensemble description of the exciplex state also reproduces an experimentally observed red shift of the emission spectrum of [OPP-4−TEA]∗ relative to [OPP-3−TEA]∗. The workflow developed here streamlines otherwise labor-intensive calculations that would require significant user intervention.

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Spectroscopic analysis of vibrational coupling in multi-molecular excited states

Abstract: Multi-molecular excited states accompanied by an intra- and inter-molecular geometric relaxation are commonly encountered in optical and electrooptical studies and applications of organic semiconductors as, for example excimers or charge...

Cited by 7 publications

References 72 publications

Exploring Highly Efficient Broadband Self‐Trapped‐Exciton Luminophors: from 0D to 3D Materials

Exploring Highly Efficient Broadband Self‐Trapped‐Exciton Luminophors: from 0D to 3D Materials

Impact of Local and Nonlocal Vibronic Coupling on the Absorption and Emission Spectra of J- and H-Dimers

Simulating Excited-State Complex Ensembles: Fluorescence and Solvatochromism in Amine-Arene Exciplexes

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