Charge-transfer interactions—their manifestations in electroabsorption spectra

Petelenz, Piotr

doi:10.1016/j.jlumin.2004.08.028

Cited by 7 publications

(2 citation statements)

References 17 publications

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“…Support for this kind of model, where local excitations mix with more separated electron–hole pair configurations, comes from electroabsorption measurements. , Analysis of electroabsorption data can reveal the interplay in the absorption spectrum of LE and CT configurations, particularly when they are weakly mixed, and thus is perhaps the most direct probe of the exciton manifold. Exciton states containing significant weights of CT configurations are known as charge-transfer excitons (CTXs).…”

Section: Introduction To Nanoscale Excitonsmentioning

confidence: 99%

Insights into Excitons Confined to Nanoscale Systems: Electron–Hole Interaction, Binding Energy, and Photodissociation

2008

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The characteristics of nanoscale excitons--the primary excited states of nanoscale systems like conjugated polymers, molecular aggregates, carbon nanotubes, and nanocrystalline quantum dots--are examined through exploration of model systems. On the basis of a valence bond-type model, an intuition is developed for understanding and comparing nanoscale systems. In particular, electron-hole interactions are examined in detail, showing how and why they affect spectroscopy and properties such as binding energy. The relationship between the bound exciton states and the nanoscale analogue of free carriers (charge-transfer exciton states) is developed. It is shown why the electron and hole act as independent particles in this manifold of states. The outlook for the field is discussed on the basis of the picture developed in the paper, with an emphasis on exciton binding and photodissociation.

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Section: Introduction To Nanoscale Excitonsmentioning

confidence: 99%

Insights into Excitons Confined to Nanoscale Systems: Electron–Hole Interaction, Binding Energy, and Photodissociation

2008

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“…in the same energy range. Electroabsorption (EA) spectroscopy , offers a way of enhancing the optical cross section of CT states relative to local or Frenkel (FR) excitations by exploiting the large Stark shift of their excited state dipole moments in a static external electric field. In EA spectroscopy, changes in the optical absorption spectrum of a thin film induced by a low frequency applied electric field are measured.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic Identification of the Charge Transfer State in Thiophene/Fullerene Heterojunctions: Electroabsorption Spectroscopy from GW/BSE Calculations

Sahoo

Patterson

2023

J. Phys. Chem. C

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Creation of charge transfer (CT) states in bulk heterojunction systems such as C60/polymer blends is an important intermediate step in the creation of carriers in organic photovoltaic systems. CT states generally have small oscillator strengths in linear optical absorption spectroscopy owing to limited spatial overlap of electron and hole wave functions in the CT excited state. Electroabsorption spectroscopy (EA) exploits changes in wave function character of CT states in response to static electric fields to enhance detection of CT states via nonlinear optical absorption spectroscopies. A 4 × 4 model Hamiltonian is used to derive splittings of even and odd Frenkel (FR) excited states and changes in wave function character of CT excited states in an external electric field. These are used to explain why FR and CT states yield EA lineshapes which are first and second derivatives of the linear optical absorption spectrum. The model is applied to ammonia–borane molecules and pairs of molecules with large and small B–N separations and CT or FR excited states. EA spectra are obtained from differences in linear optical absorption spectra in the presence or absence of a static electric field and from perturbative sum over states (SOS) configuration interaction singles χ(2) and χ(3) nonlinear susceptibility calculations. Good agreement is found between finite field (FF) and SOS methods at field strengths similar to those used in EA experiments. EA spectra of three C60/oligothiophene complexes are calculated using the SOS method combined with GW/BSE methods. For these C60/oligothiophene complexes, we find several CT states in a narrow energy range in which charge transfer from the thiophene HOMO level to several closely spaced C60 acceptor levels yields an EA signal around 10% of the signal from oligothiophene.

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The effects of light-induced reduction of the photosystem II reaction center

et al. 2009

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Accumulation of reduced pheophytin a (Pheo-D1) in photosystem II reaction center (PSII RC) under illumination at low redox potential is accompanied by changes in absorbance and circular dichroism spectra. The temperature dependences of these spectral changes have the potential to distinguish between changes caused by the excitonic interaction and temperature-dependent processes. We observed a conformational change in the PSII RC protein part and changes in the spatial positions of the PSII RC pigments of the active D1 branch upon reduction of Pheo-D1 only in the case of high temperature (298 K) dynamics. The resulting absorption difference spectra of PSII RC models equilibrated at temperatures of 77 K and 298 K were highly consistent with our previous experiments in which light-induced bleaching of the PSII RC absorbance spectrum was observable only at 298 K. These results support our previous hypothesis that Pheo-D1 does not interact excitonically with the other chlorins of the PSII RC, since the reduced form of Pheo-D1 causes absorption spectra bleaching only due to temperature-dependent processes.

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Charge-transfer interactions—their manifestations in electroabsorption spectra

Cited by 7 publications

References 17 publications

Insights into Excitons Confined to Nanoscale Systems: Electron–Hole Interaction, Binding Energy, and Photodissociation

Insights into Excitons Confined to Nanoscale Systems: Electron–Hole Interaction, Binding Energy, and Photodissociation

Spectroscopic Identification of the Charge Transfer State in Thiophene/Fullerene Heterojunctions: Electroabsorption Spectroscopy from GW/BSE Calculations

The effects of light-induced reduction of the photosystem II reaction center

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