Wurtzite silicon as a potential absorber in photovoltaics - Tailoring the optical absorption by applying strain
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-07-20 |
| Journal | Physical Review B |
| Authors | Claudia Rödl, Tobias Sander, F. Bechstedt, Julien Vidal, PÀr Olsson |
| Institutions | Centre National de la Recherche Scientifique, Friedrich Schiller University Jena |
| Citations | 71 |
Abstract
Section titled âAbstractâWe present ab initio calculations of the electronic structure and the optical properties of wurtzite Si (Si-IV). We find an indirect band gap of 0.95 eV $({\mathrm{\ensuremath{\Gamma}}}{5}\ensuremath{\rightarrow}{M}{1})$ and an optically forbidden direct gap of 1.63 eV $({\mathrm{\ensuremath{\Gamma}}}{5}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Gamma}}}{10})$, which is due to a backfolding of the ${L}_{1}$ state of Si in the diamond structure (Si-I). Optical absorption spectra including excitonic and local-field effects are calculated. Further, the effects of hydrostatic pressure, uniaxial strain, and biaxial strain on the absorption properties are investigated. Biaxial tensile strains enhance the optical absorption of Si-IV in the spectral range which is relevant for photovoltaic applications. High biaxial tensile strains $(>4%)$ even transform Si-IV into a direct semiconductor.