TY - JOUR
T1 - Structural and Electronic Modification of Photovoltaic SnS by Alloying
AU - Lany, Stephan
AU - Francis, J.
AU - Kokenyesi, R.
AU - Tate, J.
AU - Vidal, J.
PY - 2014/3/21
Y1 - 2014/3/21
N2 - 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 Sn1-x(II)xS (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., 0.6-1.5eV for Ca and Sr alloying. We subsequently synthesized such Sn1-x(Ca) xS films by pulsed laser deposition, confirmed the cubic rock-salt structure, and observed optical band gaps between 1.1 and 1.3eV. These results highlight the potential of structural modification by alloying as a route to widen the otherwise limited materials base for promising earth-abundant materials.
AB - 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 Sn1-x(II)xS (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., 0.6-1.5eV for Ca and Sr alloying. We subsequently synthesized such Sn1-x(Ca) xS films by pulsed laser deposition, confirmed the cubic rock-salt structure, and observed optical band gaps between 1.1 and 1.3eV. These results highlight the potential of structural modification by alloying as a route to widen the otherwise limited materials base for promising earth-abundant materials.
UR - http://www.scopus.com/inward/record.url?scp=84897879730&partnerID=8YFLogxK
U2 - 10.1063/1.4868974
DO - 10.1063/1.4868974
M3 - Article
AN - SCOPUS:84897879730
SN - 0021-8979
VL - 115
JO - Journal of Applied Physics
JF - Journal of Applied Physics
IS - 11
M1 - 113507
ER -