Direct band gap silicon allotropes.

Elemental silicon has a large impact on the economy of the modern world and is of fundamental importance in the technological field, particularly in solar cell industry. The great demand of society for new clean energy and the shortcomings of the current silicon solar cells are calling for new materials that can make full use of the solar power. In this paper, six metastable allotropes of silicon with direct or quasidirect band gaps of 0.39-1.25 eV are predicted by ab initio calculations at ambient pressure. Five of them possess band gaps within the optimal range for high converting efficiency from solar energy to electric power and also have better optical properties than the Si-I phase. These Si structures with different band gaps could be applied to multiple p-n junction photovoltaic modules.

[1]  A. D. Vos,et al.  Detailed balance limit of the efficiency of tandem solar cells , 1980 .

[2]  Delley,et al.  Quantum confinement in Si nanocrystals. , 1993, Physical review. B, Condensed matter.

[3]  R. H. Wentorf,et al.  Two New Forms of Silicon , 1963, Science.

[4]  Masanori Murakami,et al.  Development of refractory ohmic contact materials for gallium arsenide compound semiconductors , 2002 .

[5]  O. Sankey,et al.  Synthesis and X-Ray Characterization of Silicon Clathrates , 1999 .

[6]  Hui Wang,et al.  Tetragonal allotrope of group 14 elements. , 2012, Journal of the American Chemical Society.

[7]  X. Blase.  Quasiparticle band structure and screening in silicon and carbon clathrates , 2003 .

[8]  H. Queisser,et al.  Detailed Balance Limit of Efficiency of p‐n Junction Solar Cells , 1961 .

[9]  Li-Min Wang,et al.  Novel superhard carbon: C-centered orthorhombic C8. , 2011, Physical review letters.

[10]  Martin A. Green,et al.  Crystalline and thin-film silicon solar cells: state of the art and future potential , 2003 .

[11]  S. Koenig,et al.  Annealing of nanoindentation-induced high pressure crystalline phases created in crystalline and amorphous silicon , 2009 .

[12]  Su-Huai Wei,et al.  Towards direct-gap silicon phases by the inverse band structure design approach. , 2013, Physical review letters.

[13]  Derek L. Patton,et al.  Low-density framework form of crystalline silicon with a wide optical band gap , 2000 .

[14]  S. Louie,et al.  Electronic and optical properties of body-centered-tetragonal Si and Ge , 2010 .

[15]  Isao Tanaka,et al.  First-principles calculations of the ferroelastic transition between rutile-type and CaCl2-type SiO2 at high pressures , 2008 .

[16]  Yury Gogotsi,et al.  Thermal stability of metastable silicon phases produced by nanoindentation , 2004 .

[17]  Paulo Roberto Mei,et al.  New processes for the production of solar-grade polycrystalline silicon: A review , 2008 .

[18]  Bjørn Petter Jelle,et al.  Building integrated photovoltaic products: A state-of-the-art review and future research opportunities , 2012 .

[19]  G. Scuseria,et al.  Hybrid functionals based on a screened Coulomb potential , 2003 .

[20]  B. Malone,et al.  Ab initiosurvey of the electronic structure of tetrahedrally bonded phases of silicon , 2008 .

[21]  Stefan Goedecker,et al.  Low-energy silicon allotropes with strong absorption in the visible for photovoltaic applications , 2012, 1203.5669.

[22]  Louie,et al.  First-principles theory of quasiparticles: Calculation of band gaps in semiconductors and insulators. , 1985, Physical review letters.

[23]  Lawrence L. Kazmerski,et al.  Solar Photovoltaics R&D at the Tipping Point: A 2005 Technology Overview , 2006 .

[24]  G. J. Snyder,et al.  Thermochemistry, morphology, and optical characterization of germanium allotropes , 2014 .

[25]  A. G. Cullis,et al.  Visible light emission due to quantum size effects in highly porous crystalline silicon , 1991, Nature.

[26]  J. Kasper,et al.  Clathrate Structure of Silicon Na8Si46 and NaxSi136 (x < 11) , 1965, Science.

[27]  A. Karttunen,et al.  Bulk Synthesis and Structure of a Microcrystalline Allotrope of Germanium (m-allo-Ge) , 2011 .

[28]  Li Zhu,et al.  CALYPSO: A method for crystal structure prediction , 2012, Comput. Phys. Commun..

[29]  Yanchao Wang,et al.  Crystal structure prediction via particle-swarm optimization , 2010 .

[30]  Crain,et al.  Reversible pressure-induced structural transitions between metastable phases of silicon. , 1994, Physical review. B, Condensed matter.

[31]  Ohno,et al.  Intrinsic origin of visible light emission from silicon quantum wires: Electronic structure and geometrically restricted exciton. , 1992, Physical review letters.

[32]  Kresse,et al.  Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. , 1996, Physical review. B, Condensed matter.

[33]  Ian L. Spain,et al.  New metastable phases of silicon , 1986 .

[34]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.