Electronic and Optical Properties of Novel Phases of Silicon and Silicon-Based Derivatives

ORAL

Abstract

The vast majority of solar cells in the market today are made from crystalline silicon in the diamond-cubic phase. Nonetheless, diamond-cubic Si has an intrinsic disadvantage: it has an indirect band gap with a large energy difference between the direct gap and the indirect gap. In this work, we perform a careful study of the electronic and optical properties of a newly discovered cubic-Si$_{20} $ phase of Si that is found to sport a direct band gap. In addition, other silicon-based derivatives have also been discovered and found to be thermodynamically metastable. We carry out \textit{ab initio} GW and GW-BSE calculations for the quasiparticle excitations and optical spectra, respectively, of these new phases of silicon and silicon-based derivatives. This work was supported by NSF grant No. DMR10-1006184 and U.S. DOE under Contract No. DE-AC02-05CH11231. Computational resources have been provided by DOE at Lawrence Berkeley National Laboratory's NERSC facility and the NSF through XSEDE resources at NICS.

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Authors

  • Chin Shen Ong

    University of California at Berkeley

  • Sangkook Choi

    University of California at Berkeley

  • Steven.G. Louie

    Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory, UC Berkeley physics/ LBNL MSD, Dept. of Physics UC Berkeley and Lawrence Berkeley National Lab, University of California - Berkeley, Lawrence Berkeley National Laboratory, Physics Department, UC Berkeley and Lawrence Berkeley National Lab, University of California at Berkeley, University of California, Berkeley, UC Berkeley and Lawrence Berkeley National Laboratory, Univ of California - Berkeley, Dept. of Physics, University of California, Berkeley and Materials Science Division, Lawrence Berkeley National Laboratory