Comparative electroabsorption studies of organic and inorganic solids

Weiser, G.

doi:10.1016/j.jlumin.2004.08.008

Cited by 12 publications

(9 citation statements)

References 28 publications

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“…To better study the PM6:Y6 system, we conducted detailed measurements using EA. As has been reported, EA is a modulation spectroscopy capable of studying the electronic structure of molecular semiconductors . With an external electric field, the EA phenomenon of molecular semiconductors is explained by the Stark effect.…”

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confidence: 87%

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Direct Observation of the Charge Transfer States from a Non-Fullerene Organic Solar Cell with a Small Driving Force

Wan

Chen

Liu

et al. 2021

J. Phys. Chem. Lett.

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For organic solar cells (OSCs), the charge generation mechanism and the recombination loss are heavily linked with charge transfer states (CTS). Measuring the energy of CTS (E CT) by the most widely used technique, however, has become challenging for the non-fullerene-based OSCs with a small driving force, resulting in difficulty in the understanding of OSC physics. Herein, we present a study of the PM6:Y6 bulk heterojunction. It is demonstrated that electro-absorption can not only reveal the dipolar nature of Y6 but also resolve the morphology-dependent absorption signal of CTS in the sub-bandgap region. The device with the optimum blending weight ratio shows an E CT of 1.27 eV, which is confirmed by independent measurements. Because of the charge transfer characteristics of Y6, the charge generation at PM6:Y6 interfaces occurs efficiently under a small but non-negligible driving force of 0.14 eV, and the total recombination loss is as low as 0.43 eV.

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confidence: 87%

“…As has been reported, EA is a modulation spectroscopy capable of studying the electronic structure of molecular semiconductors. 32 With an external electric field, the EA phenomenon of molecular semiconductors is explained by the Stark effect. The shift of S1 level (ΔE) can be derived using the second-order perturbation theory.…”

mentioning

confidence: 99%

Direct Observation of the Charge Transfer States from a Non-Fullerene Organic Solar Cell with a Small Driving Force

Wan

Chen

Liu

et al. 2021

J. Phys. Chem. Lett.

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“…This is because the charge transfer process involves two dissimilar molecules, such that the wavefunction overlap between the ground state (donor HOMO) and excited state (acceptor LUMO) is weak. In spite of this, the transitions can often be observed using sensitive absorption‐related techniques such as lock‐in detection of OPV external quantum efficiency, Fourier‐transform photocurrent spectroscopy, photothermal deflection spectroscopy, electroabsorption, and emission‐related techniques like electroluminescence or photoluminescence . Several common experimental techniques used to probe CT state spectra are presented in Table 1 .…”

Section: Experimental Techniques For Probing Ct State Energiesmentioning

confidence: 99%

The Impact of Local Morphology on Organic Donor/Acceptor Charge Transfer States

Lin

Fusella

Rand

2018

Advanced Energy Materials

113

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A major breakthrough in the field of organic photovoltaics (OPVs) was the development of the donor/acceptor heterojunction that aids in separating Coulombically bound excitons that are generated upon photoabsorption. Additionally, bound charge transfer (CT) states that result from the exchange of charge carriers across the donor/acceptor interface are believed to play an important role in charge generation. Though organic thin films are often disordered, enhancements to the local structural order at the donor/acceptor interface have recently been shown to greatly influence CT state energetics and the charge generation process. In this progress report, recent efforts to understand the role that donor/acceptor morphology plays in the behavior of CT states and the resulting implications on OPV function are presented. It is aimed to provide a survey of different experimental approaches and to present a balanced examination of current interpretations of key results, and to offer best practices for the fabrication and study of morphologically tunable donor/acceptor CT states.

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“…In this case, a dithered reverse bias is applied to the device to produce a -directed electric field, F z = F DC + F AC cos( ωt ), and the change in absorption, , is detected synchronously at the modulation frequency ω . In contrast to the usual quadratic Stark effect observed in the excitonic region of the EA spectrum (not shown), the low-energy CT-related signal arises from the linear Stark effect owing to the net CT state alignment 36 . On the basis of the apparent change in oscillator strength observed for the lowest-energy CT transition, we estimate its associated dipole moment (see Supplementary Note 3 for details).…”

Section: Resultsmentioning

confidence: 70%

Sub-wavelength modulation of χ(2) optical nonlinearity in organic thin films

et al. 2017

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Modulating the second-order nonlinear optical susceptibility (χ(2)) of materials at the nanoscale represents an ongoing technological challenge for a variety of integrated frequency conversion and nonlinear nanophotonic applications. Here we exploit the large hyperpolarizability of intermolecular charge transfer states, naturally aligned at an organic semiconductor donor–acceptor (DA) interface, as a means to control the magnitude and sign of χ(2) at the nanoscale. Focusing initially on a single pentacene-C60 DA interface, we confirm that the charge transfer transition is strongly aligned orthogonal to the heterojunction and find that it is responsible for a large interfacial nonlinearity probed via second harmonic generation that is sufficient to achieve d33>10 pm V−1, when incorporated in a non-centrosymmetric DA multilayer stack. Using grating-shadowed oblique-angle deposition to laterally structure the DA interface distribution in such multilayers subsequently enables the demonstration of a χ(2) grating with 280 nm periodicity, which is the shortest reported to date.

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Comparative electroabsorption studies of organic and inorganic solids

Cited by 12 publications

References 28 publications

Direct Observation of the Charge Transfer States from a Non-Fullerene Organic Solar Cell with a Small Driving Force

Direct Observation of the Charge Transfer States from a Non-Fullerene Organic Solar Cell with a Small Driving Force

The Impact of Local Morphology on Organic Donor/Acceptor Charge Transfer States

Sub-wavelength modulation of χ(2) optical nonlinearity in organic thin films

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