Selective excitation of exciton transitions in PTCDA crystals and films

Gangilenka, V. R.; Titova, Lyubov V.; Smith, L. M.; Wägner, Hans; DeSilva, L. Ajith; Gisslén, L.; Scholz, Reinhard

doi:10.1103/physrevb.81.155208

Cited by 28 publications

(26 citation statements)

References 38 publications

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“…The present analysis, however, shows that the involved states are not purely neutral in character but have admixtures of CT character. This is in line with recent works of Scholz et al,31, 82 which, however, does not consider anharmonic potentials.…”

Section: Resultssupporting

confidence: 92%

Assessment of TD‐DFT‐ and TD‐HF‐based approaches for the prediction of exciton coupling parameters, potential energy curves, and electronic characters of electronically excited aggregates

et al. 2011

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The reliability of linear response approaches such as time-dependent Hartree-Fock (TD-HF) and time-dependent density functional theory (TD-DFT) for the prediction of the excited state properties of 3,4;9,10-tetracarboxylic-perylene-bisimide (PBI) aggregates is investigated. A dimer model of PBI is investigated as a function of a torsional motion of the monomers, which was shown before to be an important intermolecular coordinate in these aggregates. The potential energy curves of the ground state and the two energetically lowest neutral excited and charge-transfer (CT) states were obtained with the spin-component scaling modification of the approximate coupled-cluster singles-and-doubles (SCS-CC2) method as a benchmark for dispersion corrected TD-HF and a range of TD-DFT approaches. The highly accurate SCS-CC2 results are used to assess the other, computationally less demanding methods. TD-HF predicts similar potential energy curves and transition dipole moments as SCS-CC2, as well as the correct order of neutral and CT states. This supports an exciton trapping mechanism, which was found on the basis of TD-HF data. However, the investigated TD-DFT methods provide generally the opposite character for the excited states. As a consequence, these TD-DFT results have unacceptably large errors for optical properties of these dye aggregates.

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Section: Resultssupporting

confidence: 92%

Assessment of TD‐DFT‐ and TD‐HF‐based approaches for the prediction of exciton coupling parameters, potential energy curves, and electronic characters of electronically excited aggregates

et al. 2011

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“…Variations in the electronic structure of the involved dyes were also underlined by several studies. [30, 44–51] For example, Gisslen and Scholz[33] emphasize such differences between the electronic structures of PTCDA and DIP on one side and PBI compounds on the other. Recent computations on PBI dimers also predict that the strong interaction between both types of diabatic states leads to adiabatic states with strongly mixed characters.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the electronic structure of different perylene‐based dye‐aggregates

et al. 2012

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Aggregates of functionalized polycyclic aromatic molecules like perylene derivatives differ in important optoelectronic properties such as absorption and emission spectra or exciton diffusion lengths. Although those differences are well known, it is not fully understood if they are caused by variations in the geometrical orientation of the molecules within the aggregates, variations in the electronic structures of the dye aggregates or interplay of both. As this knowledge is of interest for the development of materials with optimized functionalities, we investigate this question by comparing the electronic structures of dimer systems of representative perylene-based chromophores. The study comprises dimers of perylene, 3,4,9,10-perylene tetracarboxylic acid bisimide (PBI), 3,4,9,10-perylene tetracarboxylic acid dianhydride (PTCDA), and diindeno perylene (DIP). Potential energy curves (PECs) and characters of those electronic states are investigated which determine the optoelectronic properties. The computations use the spin-component-scaled approximate coupled-cluster second-order method (SCS-CC2), which describes electronic states of predominately neutral excited (NE) and charge transfer (CT) character equally well. Our results show that the characters of the excited states change significantly with the intermolecular orientation and often represent significant mixtures of NE and CT characters. However, PECs and electronic structures of the investigated perylene derivatives are almost independent of the substitution patterns of the perylene core indicating that the observed differences in the optoelectronic properties mainly result from the geometrical structure of the dye aggregate. It also hints at the fact that optical properties can be computed from less-substituted model compounds if a proper aggregate geometry is chosen.

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“…Monomer-based models 37,115,[117][118][119][120][121] assigned the lower band of the absorption spectrum to transitions into CT states which were computed to lie below the Frenkel state. Using ionization potentials and electron affinities and adding the electro-static attraction between anion and cation for monomer distances in the corresponding crystals, the relative energetic positions of CT states of the dimer were estimated.…”

Section: Optical Properties Of A-ptcda Filmsmentioning

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.

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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.

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Selective excitation of exciton transitions in PTCDA crystals and films

Cited by 28 publications

References 38 publications

Assessment of TD‐DFT‐ and TD‐HF‐based approaches for the prediction of exciton coupling parameters, potential energy curves, and electronic characters of electronically excited aggregates

Assessment of TD‐DFT‐ and TD‐HF‐based approaches for the prediction of exciton coupling parameters, potential energy curves, and electronic characters of electronically excited aggregates

Comparison of the electronic structure of different perylene‐based dye‐aggregates

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

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