Two-dimensional action spectroscopy of excitonic systems: Explicit simulation using a phase-modulation technique

Damtie, Fikeraddis A.; Wacker, Andreas; Pullerits, Tõnu; Karki, Khadga Jung

doi:10.1103/physreva.96.053830

Cited by 37 publications

(53 citation statements)

References 49 publications

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“…In distinction to our method for nonlinear imaging of photocurrent for identifying recombination mechanisms 34,35 , where the amplitude of the nonlinear incoherent response is used, here the phase of the photocurrent is extracted by varying the interpulse time delays. This has been shown to account for the coherent nonlinear interactions in this type of spectroscopic measurement 36,37 . For all the investigated devices here, the same setup with a temporal resolution of about 15 fs and identical experimental conditions have been used.…”

Section: Resultsmentioning

confidence: 96%

Vibronic coherence contributes to photocurrent generation in organic semiconductor heterojunction diodes

Bian

Chen

et al. 2020

Nat Commun

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Charge separation dynamics after the absorption of a photon is a fundamental process relevant both for photosynthetic reaction centers and artificial solar conversion devices. It has been proposed that quantum coherence plays a role in the formation of charge carriers in organic photovoltaics, but experimental proofs have been lacking. Here we report experimental evidence of coherence in the charge separation process in organic donor/acceptor heterojunctions, in the form of low frequency oscillatory signature in the kinetics of the transient absorption and nonlinear two-dimensional photocurrent spectroscopy. The coherence plays a decisive role in the initial~200 femtoseconds as we observe distinct experimental signatures of coherent photocurrent generation. This coherent process breaks the energy barrier limitation for charge formation, thus competing with excitation energy transfer. The physics may inspire the design of new photovoltaic materials with high device performance, which explore the quantum effects in the next-generation optoelectronic applications.

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Section: Resultsmentioning

confidence: 96%

Vibronic coherence contributes to photocurrent generation in organic semiconductor heterojunction diodes

Bian

Chen

et al. 2020

Nat Commun

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“…3. We use the conventional 2D Fourier scanning protocol27 and not the double-frequency scanning as in earlier coherently detected DQC implementations 28. Besides the diagonal peaks, distinct cross peaks are observed.…”

Section: Resultsmentioning

confidence: 99%

Before Förster. Initial excitation in photosynthetic light harvesting

et al. 2019

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Electronic 2D spectroscopy allows nontrivial quantum effects in chemistry and biology to be explored in unprecedented detail. Here, we apply recently developed fluorescence detected coherent 2D spectroscopy to study the light harvesting antenna 2 (LH2) of photosynthetic purple bacteria. The method utilizes the destructive interference between two signal components thereby uncovering cross peaks which are not visible in conventional photon-echo based 2D and transient absorption measurements. Analyses of signal generating quantum pathways leads to the conclusion that, contrary to the currently prevailing physical picture, the two weakly-coupled pigment rings of LH2 share the initial electronic excitation leading to quantum mechanical correlation between the two clearly separate bands. These results are general and have consequences for the interpretation of excited states not only in photosynthesis but in all light absorbing systems. The initial delocalization could be the key for enhancing the light harvesting efficiency via biased motion towards the energy funnel.The primary processes in photosynthesis run with nearly 100 % quantum efficiency -almost every absorbed photon leads to a charge separation event. How such high efficiency is achieved and the possible role of quantum processes in it, is currently at the center of active scientific research (1-4). One of the possible functional elements of such quantum behavior and optimization in photosynthesis is delocalization -the spatial domain coherently covered by the excited state after light absorption (5).

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“…and These experimental conditions have been previously studied by solving equations of motion including the external fields as well as their phase modulation explicitly. 30 Here, we will use an alternative approach, which is based on response functions. Using fourth-order time-dependent perturbation theory one obtains (see Suppl.…”

Section: A Feynman Diagrams For 4th Order Populationsmentioning

confidence: 99%

Using fluorescence detected two-dimensional spectroscopy to investigate initial exciton delocalization between coupled chromophores

Schröter

Pullerits

Kühn

2018

The Journal of Chemical Physics

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Förster theory describes electronic exciton energy migration in molecular assemblies as an incoherent hopping process between donor and acceptor molecules. The rate is expressed in terms of the overlap integral between donor fluorescence and acceptor absorption spectra. Typical time scales for systems like photosynthetic antennae are on the order of a few picoseconds. Prior to transfer it is assumed that the initially excited donor molecule has equilibrated with respect to the local environment. However, upon excitation and during the equilibration phase the state of the system needs to be described by the full density matrix, including coherences between donor and acceptor states. While being intuitively clear, addressing this regime experimentally has been a challenge until the recently reported advances in Fluorescence Detected Two-Dimensional Spectroscopy (FD2DS). Here, we demonstrate using fourth order perturbation theory, the conditions for the presence of donor-acceptor coherence induced cross-peaks at zero waiting time between the first and the second pair of pulses.The approach is illustrated for a heterodimer model which facilitates an analytical solution.

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Two-dimensional action spectroscopy of excitonic systems: Explicit simulation using a phase-modulation technique

Cited by 37 publications

References 49 publications

Vibronic coherence contributes to photocurrent generation in organic semiconductor heterojunction diodes

Vibronic coherence contributes to photocurrent generation in organic semiconductor heterojunction diodes

Before Förster. Initial excitation in photosynthetic light harvesting

Using fluorescence detected two-dimensional spectroscopy to investigate initial exciton delocalization between coupled chromophores

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