Germanium nanoparticles for solar energy conversion

ORAL

Abstract

We propose a strategy to enhance the efficiency of solar energy conversion by elemental germanium, by using Multiple Exciton Generation (MEG) in Ge nanoparticles with a ST12 core structure. The latter is the structure of a high pressure phase of solid Ge. MEG is more efficient in bulk Ge in the diamond phase than in several other semiconductors, e.g.\ Si. In principle it may be further improved at the nanoscale, due to an increased effective Coulomb interaction. However the electronic energy gap of semiconducting nanoparticles may be too large compared to the visible solar spectrum and their density of states (DOS) too low for efficient solar energy conversion. Using ab initio calculations we found that ST12 Ge nanoparticles of $\sim$1-2~nm exhibit high impact ionization rates and thus presumably efficient MEG, as well as a gap of $\sim$2~eV and a sizable DOS in the low energy part of the spectrum. Therefore these nanoparticles appear to be promising materials for solar energy conversion exploiting MEG.

–

Authors

  • M\'arton V\"or\"os

    Budapest University of Technology and Economics

  • S. Wippermann

    University of California - Davis, Dep. of Chemistry, University of California, Davis

  • Dario Rocca

    University of California - Davis

  • Giulia Galli

    Department of Chemistry, University of California Davis, Department of Chemistry, Department of Physics, University of California, Davis, University of California - Davis, Department of Chemistry and Department of Physics UC Davis, University of California, Davis, Department of Chemistry and Department of Physics, University of California, Davis, UC Davis, Department of Chemistry and Department of Physics, UC Davis, University of California, Davis, CA

  • Adam Gali

    Wigner Research Center for Physics, Hungarian Academy of Sciences, Institute for Solid State Physics and Optics - Hungarian Academy of Sciences

  • Gergely Zimanyi

    University of California - Davis