PBC-DFT Applied to Donor−Acceptor Copolymers in Organic Solar Cells: Comparisons between Theoretical Methods and Experimental Data

Pappenfus, Ted M.; Schmidt, Jennifer A.; Koehn, Ryan E.; Alia, Joseph D.

doi:10.1021/ma1026498

Cited by 34 publications

(30 citation statements)

References 54 publications

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“…Compared with the experimental energy values: EHOMO = -4.76 eV, ELUMO = -2.46 eV and EGap = -2.30, deviations of 7, 9.7 and 17.0 % were observed, respectively. The deviations of the calculated values from the experimental values are consistent with previous calculations carried out using DFT/B3LYP method [32][33][34]. Also, since we are mainly interested in the trends of P3HT substitution, the DFT/ B3LYP method is sufficient for this study.…”

Section: Resultssupporting

confidence: 85%

Computational Study on Optoelectronic Property Tuning of Oligothiophenes via Chemical Modifications for Solar Cell Applications

Franco¹

2018

Asian J. Chem.

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Chemical modifications in conjugated polymers offers the possibility of tuning its optoelectronic properties for various applications. In this report, the optoelectronic properties of chemically modified oligomers based on poly(3-hexylthiophene-2,5-diyl) (P3HT) were investigated via DFT and TDDFT. The study was carried out by replacing the hydrogen in the 3'-position of the bithiophene monomer unit with several substituents. The polymer properties were predicted via oligomer approach where n, was varied from 1 to 10. Various electronic and optical properties were calculated: EHOMO, ELUMO, EGap, first singlet excitation energy (EOpt) and exciton binding energy (EB). Several substituents: -CN and -F were observed to have significantly lower EHOMO/ELUMO values while having similar EGap compared to P3HT. Relevant solar cell characteristics were predicted and show that P3HT-CN and P3HT-F have significantly improved open-circuit voltage (VOC). The results suggest that P3HT-CN and P3HT-F may have overall better solar cell characteristics than P3HT.

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Section: Resultssupporting

confidence: 85%

Computational Study on Optoelectronic Property Tuning of Oligothiophenes via Chemical Modifications for Solar Cell Applications

Franco¹

2018

Asian J. Chem.

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“…The power conversion efficiencies (PCEs) of organic solar cells with DA copolymers as donor materials have exceeded 10% [11], and there is strong interest in the development of structure-property correlations that will facilitate further enhancement of the PCE. Clearly, this requires precise understanding of the nature of the primary photoexcitations of DA copolymers.Existing electronic structure calculations of DA copolymers are primarily based on the density functional theory (DFT) approach or its time-dependent version (TD-DFT) [12][13][14][15][16][17][18]. The motivations behind these calculations have largely been to understand the localized versus delocalized character of the excited state reached by ground state absorption.…”

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confidence: 99%

“…Existing electronic structure calculations of DA copolymers are primarily based on the density functional theory (DFT) approach or its time-dependent version (TD-DFT) [12][13][14][15][16][17][18]. The motivations behind these calculations have largely been to understand the localized versus delocalized character of the excited state reached by ground state absorption.…”

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confidence: 99%

Theory of Primary Photoexcitations in Donor-Acceptor Copolymers

et al. 2015

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We present a generic theory of primary photoexcitations in low band gap donor-acceptor conjugated copolymers. Because of the combined effects of strong electron correlations and broken symmetry, there is considerable mixing between a charge-transfer exciton and an energetically proximate triplet-triplet state with an overall spin singlet. The triplet-triplet state, optically forbidden in homopolymers, is allowed in donor-acceptor copolymers. For an intermediate difference in electron affinities of the donor and the acceptor, the triplet-triplet state can have stronger oscillator strength than the charge-transfer exciton. We discuss the possibility of intramolecular singlet fission from the triplet-triplet state, and how such fission can be detected experimentally.PACS numbers: 78.66. Qn, 71.20.Rv, 71.35.Cc,The primary photophysical process in polymer solar cells is photoinduced charge transfer, whereby optical excitation at the junction between a donor conjugated polymer and acceptor molecules creates a charge transfer (CT) exciton whose dissociation leads to charge carriers. The donor polymeric materials used to be homopolymers such as polythiophene which absorb in the visible range of the solar spectrum [1]. Homopolymers have recently been replaced by block copolymers whose repeat units consist of alternating donor (D) and acceptor (A) moieties [2][3][4][5][6][7][8][9][10][11]. This architecture reduces the optical gap drastically, and the DA copolymers absorb in the near infrared, where the largest fraction of the photons emitted by the Sun lie. The power conversion efficiencies (PCEs) of organic solar cells with DA copolymers as donor materials have exceeded 10% [11], and there is strong interest in the development of structure-property correlations that will facilitate further enhancement of the PCE. Clearly, this requires precise understanding of the nature of the primary photoexcitations of DA copolymers.Existing electronic structure calculations of DA copolymers are primarily based on the density functional theory (DFT) approach or its time-dependent version (TD-DFT) [12][13][14][15][16][17][18]. The motivations behind these calculations have largely been to understand the localized versus delocalized character of the excited state reached by ground state absorption. Experimentally, DA copolymers exhibit a broad low energy (LE) absorption band at ∼ 700 − 800 nm and a higher energy (HE) absorption band at ∼ 400 − 450 nm [2][3][4]. There is agreement between the computational studies that the LE band is due to CT from D to A, and the HE band is a higher π-π * excitation.Recent optical studies indicate that the above simple characterization of the LE band might be incomplete, and as in the homopolymers [19], electron correlations play a stronger role in the photophysics of the DA copolymers than envisaged within DFT approaches. Grancini et al. determined from ultrafast dynamics studies that the broad LE band in PCPDT-BT (the Supplemental Material [20] for the structures of this and other DA copolymers) is c...

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“…The density functional theory (DFT) using periodic boundary condition (PBC) with B3LYP functional and the 6‐31G(d) basis set is applied to determine the geometric and electronic structures and the corresponding energies of HOMO, LUMO, and band gap. The PBC‐DFT method, implemented in the Gaussian 03 program package,41 is a reliable method for predicting the energy gaps of D–A copolymers 42. The BDO substituent as an acceptor between two donor units (furan, thiophene, selenophene, or EDOT) of the resulting polymer does not create any geometrical twist in the polymer backbone, which results in uninterrupted π‐conjugation along polymer chain that results into small to low band gap polymers.…”

Section: Resultsmentioning

confidence: 99%

Benzooxadiazaole‐based D–A–D co‐oligomers: Synthesis and electropolymerization

Pati

Das

Zade

2012

J. Polym. Sci. A Polym. Chem.

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Four D–A–D type co‐oligomers have been synthesized by Stille condensation between monostannyl derivatives of furan/thiophene/selenophene/3,4‐ethylenedioxythiophene (EDOT) and 4,7‐dibromo‐benzo[1,2,5]oxadiazole. All these co‐oligomers were successfully electrochemically polymerized in dichloromethane and characterized by spectroelectrochemistry. All four polymers possess narrow optical band gap. Spectroelectrochemical studies of polymer films on indium tin oxide revealed that the replacement of donor EDOT with furan/thiophene/selenophene has affected the low‐energy charge‐carrier (bipolaron) formation significantly. Kinetic studies based on chronoamperometry show that the polymer P5 (EDOT‐capped benzo[1,2,5]oxadiazole system) possess better electrochromic property with high transmittance (66%) in visible region than the other copolymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

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PBC-DFT Applied to Donor−Acceptor Copolymers in Organic Solar Cells: Comparisons between Theoretical Methods and Experimental Data

Cited by 34 publications

References 54 publications

Computational Study on Optoelectronic Property Tuning of Oligothiophenes via Chemical Modifications for Solar Cell Applications

Computational Study on Optoelectronic Property Tuning of Oligothiophenes via Chemical Modifications for Solar Cell Applications

Theory of Primary Photoexcitations in Donor-Acceptor Copolymers

Benzooxadiazaole‐based D–A–D co‐oligomers: Synthesis and electropolymerization

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