Interface configuration effects on excitation, exciton dissociation, and charge recombination in organic photovoltaic heterojunction

“…Donor–acceptor systems with low energy offset and high photoluminescence show improved performance for high-open-circuit-voltage OSCs 58 , 59 . Our results exhibit that efficient electron-withdrawing terminal units with a prolonged conjugation lower the bandgap and allowed the IBRD1–IBRD6 molecules to exhibit smaller excitation energies than IBR, with greater absorption spectra in the visible region (Fig.…”

Section: Resultsmentioning

confidence: 99%

Molecular engineering of indenoindene-3-ethylrodanine acceptors with A2-A1-D-A1-A2 architecture for promising fullerene-free organic solar cells

Khalid

Momina

Imran

et al. 2021

Sci Rep

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Considering the increased demand and potential of photovoltaic devices in clean, renewable electrical and hi-tech applications, non-fullerene acceptor (NFA) chromophores have gained significant attention. Herein, six novel NFA molecules IBRD1–IBRD6 have been designed by structural modification of the terminal moieties from experimentally synthesized A2-A1-D-A1-A2 architecture IBR for better integration in organic solar cells (OSCs). To exploit the electronic, photophysical and photovoltaic behavior, density functional theory/time dependent-density functional theory (DFT/TD-DFT) computations were performed at M06/6-311G(d,p) functional. The geometry, electrical and optical properties of the designed acceptor molecules were compared with reported IBR architecture. Interestingly, a reduction in bandgap (2.528–2.126 eV), with a broader absorption spectrum, was studied in IBR derivatives (2.734 eV). Additionally, frontier molecular orbital findings revealed an excellent transfer of charge from donor to terminal acceptors and the central indenoindene-core was considered responsible for the charge transfer. Among all the chromophores, IBRD3 manifested the lowest energy gap (2.126 eV) with higher λmax at 734 and 745 nm in gaseous phase and solvent (chloroform), respectively due to the strong electron-withdrawing effect of five end-capped cyano groups present on the terminal acceptor. The transition density matrix map revealed an excellent charge transfer from donor to terminal acceptors. Further, to investigate the charge transfer and open-circuit voltage (Voc), PBDBT donor polymer was blended with acceptor chromophores, and a significant Voc (0.696–1.854 V) was observed. Intriguingly, all compounds exhibited lower reorganization and binding energy with a higher exciton dissociation in an excited state. This investigation indicates that these designed chromophores can serve as excellent electron acceptor molecules in organic solar cells (OSCs) that make them attractive candidates for the development of scalable and inexpensive optoelectronic devices.

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“…In actuality, the quantity E HOMO + ∑ i LHE i p i Δ E i means the weighted average of the electron energy after photon absorption. In organic solar cells, V OC–loss is usually divided into radiative and nonradiative parts and is approximated as 0.6 ± 0.1 V. − For DSSCs, V OC–loss has not yet been systematically studied and was not taken into account in previous calculations. The weight p i is the normalized relative transition probability of the i th excited state, where ω i is the i th excited state transition probability of the studied system, the summation is run over all excited states, and ω i (normalization) is the i th excited state transition probability of the normalized system in order to compare the relative transition probability of a set of dye sensitizers.…”

Section: Resultsmentioning

confidence: 99%

Fusing Thienyl with N-Annulated Perylene Dyes and Photovoltaic Parameters for Dye-Sensitized Solar Cells

Zhang

et al. 2020

J. Phys. Chem. A

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Due to the role of dyes in dye-sensitized solar cells (DSSCs), designing novel dye sensitizers is an effective strategy to improve the power conversion efficiency. To this end, the fundamental issue is understanding the sensitizer's trilateral relationship among its molecular structure, optoelectronic properties, and photovoltaic performance. Considering the good performance of N-annulated perlyene dye sensitizers, the geometries, electronic structures, and excitations of the selected representative organic dye sensitizers C276, C277, and C278 as well as dyes adsorbed on TiO 2 clusters were calculated in order to investigate the relationship between molecular structures and properties. It was found that fusing thienyl to N-annulated perlyene can elevate the highest occupied molecular orbital (HOMO) energy, reduce the orbital energy gap, increase the density of states, expand the HOMO to the benzothiadiazole moiety, enhance the charge transfer excitation, elongate the fluorescence lifetime, amplify the light harvesting efficiency, and induce a red-shift of the absorption spectra. The transition configurations and molecular orbitals of the dye-adsorbed systems support that the electron injection in DSSCs based on these dyes is a fast mode. Based on extensive analysis of the electronic structures and excitation properties of these dye sensitizers and the dye-adsorbed systems, we present new quantities as open-circuit voltage and short-circuit current density descriptors that celebrate the quantitative bridge between the photovoltaic parameters and the electronic structurerelated properties in order to expose the relationship between properties and performance. The results of this work are critical for the design of novel dye sensitizers for solar cells.

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Interface configuration effects on excitation, exciton dissociation, and charge recombination in organic photovoltaic heterojunction

Cited by 16 publications

References 104 publications

Molecular tuning of non-fullerene electron acceptors in organic photovoltaics: a theoretical study

Molecular tuning of non-fullerene electron acceptors in organic photovoltaics: a theoretical study

Molecular engineering of indenoindene-3-ethylrodanine acceptors with A2-A1-D-A1-A2 architecture for promising fullerene-free organic solar cells

Fusing Thienyl with N-Annulated Perylene Dyes and Photovoltaic Parameters for Dye-Sensitized Solar Cells

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