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Portrait of Heiner Linke; Photo: Kennet Ruona

Heiner Linke

Professor, Deputy dean at Faculty of Engineering, LTH

Portrait of Heiner Linke; Photo: Kennet Ruona

Reversible electron-hole separation in a hot carrier solar cell

Author

  • S. Limpert
  • S. Bremner
  • Heiner Linke

Summary, in English

Hot-carrier solar cells are envisioned to utilize energy filtering to extract power from photogenerated electron-hole pairs before they thermalize with the lattice, and thus potentially offer higher power conversion efficiency compared to conventional, single absorber solar cells. The efficiency of hot-carrier solar cells can be expected to strongly depend on the details of the energy filtering process, a relationship which to date has not been satisfactorily explored. Here, we establish the conditions under which electron-hole separation in hot-carrier solar cells can occur reversibly, that is, at maximum energy conversion efficiency. We thus focus our analysis on the internal operation of the hot-carrier solar cell itself, and in this work do not consider the photon-mediated coupling to the Sun. After deriving an expression for the voltage of a hot-carrier solar cell valid under conditions of both reversible and irreversible electrical operation, we identify separate contributions to the voltage from the thermoelectric effect and the photovoltaic effect. We find that, under specific conditions, the energy conversion efficiency of a hot-carrier solar cell can exceed the Carnot limit set by the intradevice temperature gradient alone, due to the additional contribution of the quasi-Fermi level splitting in the absorber. We also establish that the open-circuit voltage of a hot-carrier solar cell is not limited by the band gap of the absorber, due to the additional thermoelectric contribution to the voltage. Additionally, we find that a hot-carrier solar cell can be operated in reverse as a thermally driven solid-state light emitter. Our results help explore the fundamental limitations of hot-carrier solar cells, and provide a first step towards providing experimentalists with a guide to the optimal configuration of devices.

Department/s

  • Solid State Physics
  • NanoLund

Publishing year

2015

Language

English

Publication/Series

New Journal of Physics

Volume

17

Document type

Journal article

Publisher

IOP Publishing

Topic

  • Energy Systems

Keywords

  • quantum thermodynamics
  • hot carrier solar cells
  • efficiency
  • entropy
  • production
  • photovoltaics
  • thermoelectrics

Status

Published

ISBN/ISSN/Other

  • ISSN: 1367-2630