On the applicability of time‐dependent density functional theory (TDDFT) and semiempirical methods to the computation of excited‐state potential energy surfaces of perylene‐based dye‐aggregates

Walter, Christof; Krämer, Veronika; Engels, Bernd

doi:10.1002/qua.25337

Cited by 31 publications

(52 citation statements)

References 59 publications

(163 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As a result of the interactions between diabatic states, the energy profiles of the two lowest energy adiabatic states (1 B u and 1 A g ) cross several times along the shift coordinate, thereby determining an alternation of the H and J spectroscopic character of the aggregate which is not accounted for by the simpler exciton model. This peculiarity has already been pointed out in previous investigations on PBI dimers and is nicely reproduced at FOCIS level. Concerning the twisting coordinate by comparing diabatic and adiabatic energy profiles we can also identify the presence of an avoided crossing (see Supporting Information Fig.…”

Section: Resultssupporting

confidence: 81%

“…However, the dimer model, where only two dye molecules out of a larger aggregate are explicitly considered, was employed successfully to obtain parameters of the FE–CT model . Further developments of these models incorporate coarse‐gaining strategies for the determination of coupling parameters between FE and partially also CT‐configurations …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A model hamiltonian tuned toward high level ab initio calculations to describe the character of excitonic states in perylenebisimide aggregates

et al. 2018

Self Cite

View full text Add to dashboard Cite

On the example of an aggregate of two perylenebisimide (PBI) molecules the character of the lowest excited electronic states in terms of charge transfer (CT) and Frenkel exciton (FE) configurations is investigated as a function of the intermolecular arrangement. A minimal model Hamiltonian based on two FE and two CT configurations at the frontier‐orbitals CIS (FOCIS) level is shown to represent a simple and comprehensible approach providing insight into the physical significance of the model Hamiltonian matrix elements. The recently introduced analysis and diabatization procedure (Liu et al., J. Chem. Phys. 2015, 143, 084106 ) method is used to extract the energies of the configurations and their interactions (the model Hamiltonian parameters) also from the accurate CC2 approach. An analysis in terms of diabatic energy profiles and their interactions shows that the FOCIS parameters give a qualitatively correct description of the adiabatic excited state energy profiles. Comparison with CC2 reveals, however, the presence of avoided crossings at FOCIS level, associated with a large character change (CT/FE) of the excited states as a function of the aggregate structure, which represents the major drawback of FOCIS results. We show that proper amendment of the FOCIS‐derived parameters allows to accurately represent the potential energy surfaces and crossings of the excited dimer states as a function of the aggregate structure. © 2018 Wiley Periodicals, Inc.

show abstract

Section: Resultssupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

A model hamiltonian tuned toward high level ab initio calculations to describe the character of excitonic states in perylenebisimide aggregates

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…84 In previous studies we always used wave-function based approaches like SCS-CC2 because time-dependent density functional theory predicted a different order of the bright Frenkel (S 2 state) and lower CT states (S 3 ). 33,34,85 Using SCS-CC2/TZVP as benchmark, pure GGA (BLYP, PBE) and the hybrid functionals as B3LYP predicted that the CT states should lie considerably below the corresponding Frenkel states, which was in contrast to the predictions of the more accurate SCS-CC2 method. For BHLYP/ TZVP the energy difference between both states were smaller than 0.1 eV but the CT state lie still below the upper Frenkel state.…”

Section: Technical Detailscontrasting

confidence: 39%

“…It is interesting to note that more sophisticated semi-empirical methods as the OMx-approaches of Thiel and coworkers 91,92 seem to be less suitable. 85 More information about these studies can be found in Section 3.6.…”

Section: Technical Detailsmentioning

confidence: 99%

The dimer-approach to characterize opto-electronic properties of and exciton trapping and diffusion in organic semiconductor aggregates and crystals

Engels

Engel

2017

Phys. Chem. Chem. Phys.

Self Cite

View full text Add to dashboard Cite

A fundamental understanding of photo-induced processes in opto-electronic thin film devices is a prerequisite for the rational design of improved organic semiconductor materials. Absorption and emission spectra provide important insights into the complicated electronic structure of and relaxation processes in organic semiconductor aggregates and crystals. They are of interest because they often limit the efficiencies of the devices. For an assignment of the spectra a close interplay between experiment and theory is essential because simulations are often necessary to entangle the various effects which determine the features of the spectra. In the present perspective we describe the so called dimer-approach and provide a few examples in which this approach could successfully deliver an atomistic picture of photo-induced relaxation effects in perylene-based materials and characterize their optical spectra. The model Hamiltonians of standard monomer-based approaches are also briefly discussed to reveal the differences between both methods and to shed some light on their strengths and shortcomings.

show abstract

“…[42][43][44] Furthermore, it yields reliable intermolecular potential energies for dimers composed of molecular semiconductors. [45,46] In well-ordered but also in amorphous systems, excitons and charges are expected to be delocalized over several units. [2,47,48] Consequently, the computations of oligomers larger than dimers would be desirable, but such computations are too costly within the framework of the present study.…”

Section: Theoretical Approachmentioning

confidence: 99%

QM/MM calculations combined with the dimer approach on the static disorder at organic‐organic interfaces of thin‐film organic solar cells composed of small molecules

Brückner

Stolte²,

Würthner³

et al. 2017

J of Physical Organic Chem

Self Cite

View full text Add to dashboard Cite

A QM/MM approach using ωB97X-D combined with AMOEBA calculations was used to analyze the energetic disorder in the vicinity of interfaces in amorphous organic heterostructures. Distributions of ground-, excited-, and cationic-state energies as well as of ionization potentials and excitation energies, all being relevant quantities for the transport properties of thin films, were calculated. As already found for bulk amorphous organic semiconductors, local densities of states at molecular interfaces possess Gaussian-shaped profiles with a significant amount of disorder. Assuming a disorder-limited activation of exciton and charge transport, a decrease in the amount of disorder could improve the transport properties. Relating calculated disorders to molecular parameters revealed that in line with the Bässler model, especially the molecular polarity, its change upon electronic excitation, and the molecular polarizability are relevant quantities leading to energetically largely disordered films. Moreover, because of the different mechanisms of exciton and polaron delocalization, a given morphology with disordered charge-transport levels gives not necessarily rise to disordered exciton-transport levels and vice versa. | INTRODUCTIONDisorder in molecular organic semiconductors has been recognized as a key parameter limiting the semiconductor's transport properties for both charges and excitons. [1] A random distribution of the molecules in a disordered amorphous film results in considerable variations in local intermolecular interactions. This gives rise to a distribution of ionization and excitation energies, the relevant quantities for charge and exciton transport, which depend among others on these intermolecular interaction energies. [2] According to the central limit theorem, resulting densities of states (DOSs) for excitons and charges have a Gaussian shape because intermolecular interaction energies are composed of many independently varying contributions. [3] The width of the Gaussian-shaped DOSs, ie, the standard deviation of the Gaussian normal distribution σ, is referred to as the disorder parameter and characterizes the amount of site energy disorder, ie, of static disorder, in the semiconducting solid-state system. [2] Based on this Gaussian DOS, the Bässler model describes charge transport in organic semiconductors as an incoherent hopping process between the normally distributed sites. [4] The expression "disorder" can be connected with geometrical and energetical disorder. In line with the Bässler nomenclature, in the following the expression, "disorder" is always used to characterize the energetic disorder unless otherwise noted. Although experimentally detected field-and temperature-dependent charge carrier mobilities confirm the predictions of the Bässler model in principle, no direct experimental proof for the Gaussian-shaped DOS, particularly of charge carriers, in disordered molecular semiconductors † This article is published as part of a special issue to celebrate the 80 th birthday of P...

show abstract

On the applicability of time‐dependent density functional theory (TDDFT) and semiempirical methods to the computation of excited‐state potential energy surfaces of perylene‐based dye‐aggregates

Cited by 31 publications

References 59 publications

A model hamiltonian tuned toward high level ab initio calculations to describe the character of excitonic states in perylenebisimide aggregates

A model hamiltonian tuned toward high level ab initio calculations to describe the character of excitonic states in perylenebisimide aggregates

The dimer-approach to characterize opto-electronic properties of and exciton trapping and diffusion in organic semiconductor aggregates and crystals

QM/MM calculations combined with the dimer approach on the static disorder at organic‐organic interfaces of thin‐film organic solar cells composed of small molecules

Contact Info

Product

Resources

About