Identification of Ultrafast Photophysical Pathways in Photoexcited Organic Heterojunctions

Janković, Veljko; Vukmirović, Nenad

doi:10.1021/acs.jpcc.7b05582

Cited by 8 publications

(27 citation statements)

References 71 publications

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“…In addition to the MH, LJH and TCH theories, there are a number of other approaches that investigate the influence of phonons on the properties of organic solar cells. These are, among others [33,34], based on Ansatz wave functions [35], a dynamics controlled truncation scheme within the density matrix formalism [36], Green's function formalism [37] or the quantum master equation [38]. Despite their success in describing some of the aspects characteristic for electron-phonon coupled systems, these approaches usually suffer from the curse of dimensionality, i.e.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast carrier dynamics at organic donor–acceptor interfaces—a quantum-based assessment of the hopping model

et al. 2022

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We investigate the charge transfer dynamics of photogenerated excitons at the donor-acceptor interface of an organic solar cell blend under the influence of molecular vibrations. This is examined using an effective Hamiltonian, parametrized by density functional theory calculations, to describe the full quantum behaviour of the relevant molecular orbitals, which are electronically coupled with each other and coupled to over one hundred vibrations (via Holstein coupling). This electron-phonon system is treated in a numerically quasi-exact fashion using the matrix-product-state ansatz. We provide insight into different mechanisms of charge separation and their relation to the electronic driving energy for the separation process. We find ultrafast electron transfer, which for small driving energy is dominated by kinetic processes and at larger driving energies by dissipative phonon emission connected to the prevalent vibration modes. Using this fully quantum mechanical model we perform a benchmark comparison to a recently developed semi-classical hopping approach, which treats the hopping and vibration time scales consistently. We find qualitatively and quantitatively good agreement between the results of the sophisticated matrix-product-state based quantum dynamics and the simple and fast time-consistent-hopping approach.

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Section: Introductionmentioning

confidence: 99%

Ultrafast carrier dynamics at organic donor–acceptor interfaces—a quantum-based assessment of the hopping model

et al. 2022

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“…We found that the normalized PL intensity was the lowest in the “NiO x via B-OH” samples. This suggests that the exciton dissociation (or charge separation) tendency of this material is superior [78,79,80,81]. It was also found that the PCE (%) values of the devices were consistent with this tendency (Table 1).…”

Section: Resultsmentioning

confidence: 60%

Facile NiOx Sol-Gel Synthesis Depending on Chain Length of Various Solvents without Catalyst for Efficient Hole Charge Transfer in Perovskite Solar Cells

2018

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Nickel oxide (NiOx)–based perovskite solar cells (PSCs) have recently gained considerable interest, and exhibit above 20% photovoltaic efficiency. However, the reported syntheses of NiOx sol-gel used toxic chemicals for the catalysts during synthesis, which resulted in a high-temperature annealing requirement to remove the organic catalysts (ligands). Herein, we report a facile “NiOx sol-gel depending on the chain length of various solvents” method that eschews toxic catalysts, to confirm the effect of different types of organic solvents on NiOx synthesis. The optimized conditions of the method resulted in better morphology and an increase in the crystallinity of the perovskite layer. Furthermore, the use of the optimized organic solvent improved the absorbance of the photoactive layer in the PSC device. To compare the electrical properties, a PSC was prepared with a p-i-n structure, and the optimized divalent alcohol-based NiOx as the hole transport layer. This improved the charge transport compared with that for the typical 1,2-ethanediol (ethylene glycol) used in earlier studies. Finally, the optimized solvent-based NiOx enhanced device performance by increasing the short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF), compared with those of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)–based devices.

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“…Let us point out another viewpoint on the result embodied in Eq. (34). Equation ( 33) can be formally rewritten by introducing the dipole-moment hyperoperators that act the initial electronic state |g g| from the opposite sides…”

Section: General Theory Of Second-order Light-induced Dynamicsmentioning

confidence: 99%

“…The manipulations that are necessary to recast Eqs. ( 40) and (34) as HEOM presented in Eqs. ( 19) and ( 20), respectively, proceed as usually [48].…”

Section: Excitation By Weak (Coherent) Laser Pulsesmentioning

confidence: 99%

“…The DCT scheme classifies DMs according to the lowest power with which they scale in the exciting field and, therefore, provides a recipe to analyze the dynamics up to any given order in the exciting field in terms of a finite number of electronic DMs. A DCT-based approach has been recently applied by one of us to study exciton generation and subsequent charge separation in photoexcited OPVs [33,34]. However, the truncation of the environment-assisted branch of the hierarchy within the DCT scheme still has to be performed separately [31], and it is commonly done in a low order in the excitationenvironment coupling [29,33,35].…”

Section: Introductionmentioning

confidence: 99%

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Exact description of excitonic dynamics in molecular aggregates weakly driven by light

Janković,

Mančal

2020

Preprint

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We present a rigorous theoretical description of excitonic dynamics in molecular light-harvesting aggregates photoexcited by weak-intensity radiation of arbitrary properties. While the interaction with light is included up to the second order, the treatment of the excitation-environment coupling is exact and results in an exact expression for the reduced excitonic density matrix that is manifestly related to the spectroscopic picture of the photoexcitation process. This expression takes fully into account the environmental reorganization processes triggered by the two interactions with light. This is particularly important for slow environments and/or strong excitation-environment coupling. Within the exponential decomposition scheme, we demonstrate how our result can be recast as the hierarchy of equations of motion (HEOM) that explicitly and consistently includes the photoexcitation step. We analytically describe the environmental reorganization dynamics triggered by a delta-like excitation of a single chromophore, and demonstrate how our HEOM, in appropriate limits, reduces to the Redfield equations comprising a pulsed photoexcitation and the nonequilibrium Förster theory. We also discuss the relation of our formalism to the combined Born-Markov-HEOM approaches in the case of excitation by thermal light.I.

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Identification of Ultrafast Photophysical Pathways in Photoexcited Organic Heterojunctions

Cited by 8 publications

References 71 publications

Ultrafast carrier dynamics at organic donor–acceptor interfaces—a quantum-based assessment of the hopping model

Ultrafast carrier dynamics at organic donor–acceptor interfaces—a quantum-based assessment of the hopping model

Facile NiOx Sol-Gel Synthesis Depending on Chain Length of Various Solvents without Catalyst for Efficient Hole Charge Transfer in Perovskite Solar Cells

Exact description of excitonic dynamics in molecular aggregates weakly driven by light

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