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Title: Structural and electronic modification of photovoltaic SnS by alloying

Emergence of a terawatt scalable photovoltaic (PV) thin film technology is currently impeded by the limited supply of relatively rare elements like In or Te, which has spurred active research in recent years on earth-abundant PV materials. Instead of searching for alternative PV materials, we approach the problem here by structural modification through alloying of a known PV material, namely, tin sulfide. Although SnS is a strong visible light absorber that is naturally p-doped, its indirect band gap reduces the open circuit voltage of SnS-based solar cells. The anisotropic crystal structure results in undesirable anisotropic transport properties. Based on the observation that the isoelectronic sulfides MgS, CaS, and SrS assume the rock-salt structure, we use ab initio calculations to explore the structure and electronic properties of metastable Sn{sub 1−x}(II){sub x}S (II = Mg, Ca, Sr) alloys, finding that the isotropic rock-salt phase is stabilized above x = 0.2–0.3, and predicting direct band gaps in the range of interest for PV applications, i.e., 0.6–1.5 eV for Ca and Sr alloying. We subsequently synthesized such Sn{sub 1−x}(Ca){sub x}S films by pulsed laser deposition, confirmed the cubic rock-salt structure, and observed optical band gaps between 1.1 and 1.3 eV. These results highlight the potential of structural modification by alloyingmore » as a route to widen the otherwise limited materials base for promising earth-abundant materials.« less
Authors:
;  [1] ; ;  [2] ;  [3]
  1. National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401-3305 (United States)
  2. Department of Physics, Oregon State University, Corvallis, Oregon 97331 (United States)
  3. Department of Chemistry, Oregon State University, Corvallis, Oregon 97330 (United States)
Publication Date:
OSTI Identifier:
22271194
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 11; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANISOTROPY; CALCIUM SULFIDES; CRYSTAL STRUCTURE; DOPED MATERIALS; ELECTRONIC STRUCTURE; ENERGY BEAM DEPOSITION; LASER RADIATION; MAGNESIUM SULFIDES; MODIFICATIONS; PHOTOVOLTAIC EFFECT; PULSED IRRADIATION; SOLAR CELLS; STRONTIUM SULFIDES; THIN FILMS; TIN SULFIDES