Frenkel–Holstein Hamiltonian applied to absorption spectra of quaterthiophene-based 2D hybrid organic–inorganic perovskites

Abstract

For the prototypical two-dimensional hybrid organic–inorganic perovskites (2D HOIPs) (AE4T)PbX4 (X = Cl, Br, and I), we demonstrate that the Frenkel–Holstein Hamiltonian (FHH) can be applied to describe the absorption spectrum arising from the organic component. We first model the spectra using only the four nearest neighbor couplings between translationally inequivalent molecules in the organic herringbone lattice as fitting parameters in the FHH. We next use linear-response time-dependent density functional theory (LR-TDDFT) to calculate molecular transition densities, from which extended excitonic couplings are evaluated based on the atomic positions within the 2D HOIPs. We find that both approaches reproduce the experimentally observed spectra, including changes in their shape and peak positions. The spectral changes are correlated with a decrease in excitonic coupling from X = Cl to X = I. Importantly, the LR-TDDFT-based approach with extended excitonic couplings not only gives better agreement with the experimental absorption line shape than the approach using a restricted set of fitted parameters but also allows us to relate the changes in excitonic coupling to the underlying geometry. We accordingly find that the decrease in excitonic coupling from X = Cl to Br to I is due to an increase in molecular separation, which in turn can be related to the increasing Pb–X bond length from Cl to I. Our research opens up a potential pathway to predicting optoelectronic properties of new 2D HOIPs from ab initio calculations and to gain insight into structural relations from 2D HOIP absorption spectra.

Connecting the Dots for Fundamental Understanding of Structure-Photophysics-Property Relationships of COFs, MOFs, and Perovskites using a Multiparticle Holstein Formalism

“…In Ref. 311, the interactions between the organic and inorganic excitons in AE4TPbX 4 was assumed to be negligible. Despite this approximation, the theoretical study reported in Ref.…”

“…7 show that simulations using the MHF reproduce the vibronic progression arising from the organic component in (AE4T)PbX 4 (X = Cl, Br, and I). 311 It was also found that the choice of the halide ion in the inorganic component plays a central role in determining the shape of the vibronic structure observed in oligothiophene based perovskites. 311 The transition spacings in the excitonic spectra seem to directly correlate with the choice of the organic spacer.…”

“…311 It was also found that the choice of the halide ion in the inorganic component plays a central role in determining the shape of the vibronic structure observed in oligothiophene based perovskites. 311 The transition spacings in the excitonic spectra seem to directly correlate with the choice of the organic spacer. While transition spacings of 14 meV and 40 meV were observed in the presence of aliphatic chains 312,313 and phenyl groups, 152,235,236,314 respectively, the presence of oligothiophene cations in (AE4T)PbX 4 results in a distinct progression having a transition spacing equal to the aromatic-to-quinoidal vibrational energy of ∼0.17 absorption and emission spectra.…”

Accurate Modeling of Excitonic Coupling in Cyanine Dye Cy3

“…In analogy to the classical decomposition of the electronic density into point charges localized on the atoms’ nuclear centers, we can decompose the electronic transition density into atomic transition charges centered on the atomic centers (tqs). ,,− Hence, eq becomes N K and N L are the number of atoms in each chromophore, and R I , R J are the nuclear coordinates. Mulliken population analysis has been used extensively to derive the atomic transition charges from the electronic transition density matrix between ground and excited singlet state the same way we would use it to derive the classical partial charges from the electronic density matrix of a single state. ,, In the Mulliken-based treatment, we use the transition density matrix between the ground and an excited state to calculate the atomic transition charges in a similar way as it is done for the electron density of an individual electronic state. , In this approach, electrons associated with basis functions centered on a given atom are used in calculating the partial charge of that atom, while electrons “shared” between basis functions centered on different atoms are divided evenly between the two atoms.…”

Analog Quantum Simulation of the Dynamics of Open Quantum Systems with Quantum Dots and Microelectronic Circuits

“…For the system-bath interaction, we consider the archetypical spin-boson and displaced harmonic oscillator (or Frenkel-Holstein) models as they have been found to be useful to describe a variety of problems. This includes quantum impurity problems, [52] quantum thermodynamics [53], artificial light-matter coupling [54] for the spin-boson coupling, and molecular photophysics such as the dynamics of natural [55] and artificial chromophore aggregates, [56] photo-voltaic materials, [57] and electro-luminescent materials [58] for the displaced harmonic oscillator.…”