On the origin of the open-circuit voltage of polymer–fullerene solar cells

Vandewal, Koen; Tvingstedt, Kristofer; Gadisa, Abay; Inganäs, Olle; Manca, Jean

doi:10.1038/nmat2548

Cited by 1,180 publications

(1,280 citation statements)

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“…28 The alternative model for the CT absorption proposes that the shape arises from a strong electron−phonon coupling, with a line-shape given by Marcus theory. 29 Analysis of the shape and the associated emission band leads to a CT energy of 1.14 eV for P3HT:PCBM. Earlier data by Vandewal et al 30 positioned E GI at a significantly lower energy than more recent data.…”

Section: Background and Measurement Methodologymentioning

confidence: 99%

Electronic Structure and Transition Energies in Polymer–Fullerene Bulk Heterojunctions

et al. 2014

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Photocurrent spectroscopy is used to measure both the charge transfer and exciton optical absorption spectra of various bulk heterojunction organic solar cells. The energy difference between the polymer HOMO energy and the fullerene LUMO energy is obtained from the spectra, along with the disorder energy. Combining information from cells with several different polymers and fullerenes allows measurements of the energy differences between HOMO or LUMO energies for about 10 different polymers and fullerenes, with an estimated uncertainty of 50 meV. Heterojunction band offsets are obtained for the various cells, distinguishing between the excitonic and the single-carrier band offsets. The cell open-circuit voltage is shown to be closely correlated with the interface band gap. The exciton disorder energy is directly correlated to the band-tail disorder and we also consider the effects of exciton thermalization on the charge generation mechanism. The data indicate that an energy offset between the polymer exciton and the charge transfer ground state below about 0.25 eV adversely affects the cell performance, while a HOMO band offset below about 0.2−0.3 eV also degrades cell performance but by a different mechanism.

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Section: Background and Measurement Methodologymentioning

confidence: 99%

Electronic Structure and Transition Energies in Polymer–Fullerene Bulk Heterojunctions

et al. 2014

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“…64 Evidence for such intermediate charge transfer states has been presented for a number of other blend systems including PCPDTBT:PCBM. 65 The appearance of CT states is in general a function of blend composition and therefore of microstructure. In the case of PCPDTBT:PCBM, the yield of long-lived mobile carriers originating from this intermediate state is found to be sensitive to the blend ratio, with a maximum at the ratio which yields the highest PCE in devices.…”

Section: Blend Compositionmentioning

confidence: 99%

Influence of blend microstructure on bulk heterojunction organic photovoltaic performance

et al. 2011

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This tutorial review discusses the factors influencing blend microstructure and performance in bulk heterojunction organic photovoltaic cells.Please check this proof carefully. Our staff will not read it in detail after you have returned it. Translation errors between word-processor files and typesetting systems can occur so the whole proof needs to be read. Please pay particular attention to: tabulated material; equations; numerical data; figures and graphics; and references. If you have not already indicated the corresponding author(s) please mark their name(s) with an asterisk. Please e-mail a list of corrections or the PDF with electronic notes attached --do not change the text within the PDF file or send a revised manuscript.Please bear in mind that minor layout improvements, e.g. in line breaking, table widths and graphic placement, are routinely applied to the final version.Please note that, in the typefaces we use, an italic vee looks like this: n, and a Greek nu looks like this: n.We will publish articles on the web as soon as possible after receiving your corrections; no late corrections will be made.Please return your final corrections, where possible within 48 hours of receipt, by e-mail to: chemsocrev@rsc.org Reprints-Electronic (PDF) reprints will be provided free of charge to the corresponding author. Enquiries about purchasing paper reprints should be addressed via: http://www.rsc.org/Publishing/ReSourCe/PaperReprints/. Costs for reprints are below: Q3The sentence beginning ''For example it has been shown. . .'' has been altered for clarity, please check that the meaning is correct. Q4The citation to ' Fig. 8(a)' in the sentence beginning 'Grazing-incidence X-ray diffraction (XRD) measurements. . .' has been changed to ' Fig. 10(a)' as the text appears to discuss ' Fig. 10(a)'. Please check that this is correct. Q5The citation to ' Fig. 8(b)' in the sentence beginning 'Upon annealing, P3HT chains begin to crystallize. . .' has been changed to ' Fig The performance of organic photovoltaic devices based upon bulk heterojunction blends of donor and acceptor materials has been shown to be highly dependent on the thin film microstructure. In this tutorial review, we discuss the factors responsible for influencing blend microstructure and how these affect device performance. In particular we discuss how various molecular design approaches can affect the thin film morphology of both the donor and acceptor components, as well as their blend microstructure. We further examine the influence of polymer molecular weight and blend composition upon device performance, and discuss how a variety of processing techniques can be used to control the blend microstructure, leading to improvements in solar cell efficiencies.

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“…38 Both techniques demonstrated photocurrent signal below the bandgap of pristine materials, indicating absorption from the CT state. [37][38][39][40][41] Photoluminescence Photon absorption by the polymer (fullerene) generates excitons, which transfer electrons to the fullerene and leave holes in the polymer (or the other way around). The electrons in the fullerene might radiatively recombine with the holes in the polymer at the donor/acceptor interfaces, generating additional photoluminescence (PL) which is absent in the PL spectra of the individual components.…”

Section: Absorptionmentioning

confidence: 99%

Charge generation in polymer–fullerene bulk-heterojunction solar cells

Gao

Inganäs

2014

Phys. Chem. Chem. Phys.

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204

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Charge generation in organic solar cells is a fundamental yet heavily debated issue. This article gives a balanced review of different mechanisms proposed to explain efficient charge generation in polymer-fullerene bulk-heterojunction solar cells. We discuss the effect of charge-transfer states, excess energy, external electric field, temperature, disorder of the materials, and delocalisation of the charge carriers on charge generation. Although a general consensus has not been reached yet, recent findings, based on both steady-state and transient measurements, have significantly advanced our understanding of this process.2

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On the origin of the open-circuit voltage of polymer–fullerene solar cells

Cited by 1,180 publications

References 40 publications

Electronic Structure and Transition Energies in Polymer–Fullerene Bulk Heterojunctions

Electronic Structure and Transition Energies in Polymer–Fullerene Bulk Heterojunctions

Influence of blend microstructure on bulk heterojunction organic photovoltaic performance

Charge generation in polymer–fullerene bulk-heterojunction solar cells

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