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Reply to ‘Ideal solar cell efficiencies’

Nature Photonics volume 15, pages 165–166 (2021)Cite this article

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Guillemoles et al. reply — We wrote our Comment1 as a brief and concise guide to the Shockley–Queisser (SQ) model2, chiefly aiming to explain how real-world solar cells (non-concentrating, single-junction) must be related to the efficiency limits that result from the SQ model. There is a need for such a Comment, especially in the context of a widened portfolio of new very efficient solar cell materials and a rapidly growing community. As obvious from the title1, we target non-specialist readers. Such approach3 has the risk that the resulting text is unsatisfactory for specialist readers. The author of the Correspondence on our Comment4 is certainly such specialist reader. Thus, to reply to the Correspondence we need to leave the level at which we presented the topic in our Comment, to make clear that while there can be differences of opinion as how to explain the issue to the ‘perplexed’, what is written in our comment is a valid description of the SQ model.

The most important issue brought up in the Correspondence, and the one we concentrate on in our reply, is the role of étendue expansion as a main loss, especially in the case where all recombination is radiative. In ref. 1, we introduced the term ‘isothermal losses’ for the actual heat generation (loss of total, that is, internal, energy per incoming photon) that occurs in the device in addition to the initial non-absorption and thermalization losses. Étendue losses, in contrast, refer specifically to the entropy increase associated with photon exchange between the sun, the device and the environment. Étendue expansion refers to the fact that the étendue \(\varepsilon _{{\mathrm{in}}}\) of the incoming solar radiation differs by a factor of ~46,000 from that of the outgoing radiation (emitted by the solar cell), \(\varepsilon _{{\mathrm{out}}}\), if no additional measures are in place to either concentrate the light or limit the solid angle of the emitted radiation.

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Fig. 1: Power losses in the SQ model including the effect of étendue expansion.

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Authors and Affiliations

  1. CNRS, UMR 9006, Institut Photovoltaique d’Ile de France (IPVF), Palaiseau, France

    Jean-Francois Guillemoles

  2. IEK5-Photovoltaik, Forschungszentrum Jülich, Jülich, Germany

    Thomas Kirchartz & Uwe Rau

  3. Fac. of Engineering and CENIDE, Univ. of Duisburg-Essen, Duisburg, Germany

    Thomas Kirchartz

  4. Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth, Israel

    David Cahen

Authors
  1. Jean-Francois Guillemoles
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  2. Thomas Kirchartz
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  3. David Cahen
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  4. Uwe Rau
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Correspondence to Jean-Francois Guillemoles, Thomas Kirchartz, David Cahen or Uwe Rau.

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Guillemoles, JF., Kirchartz, T., Cahen, D. et al. Reply to ‘Ideal solar cell efficiencies’. Nat. Photonics 15, 165–166 (2021). https://doi.org/10.1038/s41566-021-00775-1

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