TY - JOUR
T1 - Role of Na and Ca as Isovalent Dopants in Cu2ZnSnS4 Solar Cells
AU - Berman, Samuel
AU - Sai Gautam, Gopalakrishnan
AU - Carter, Emily Ann
N1 - Funding Information:
E.A.C. thanks the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award No. DESC0002120 for funding this project.
Publisher Copyright:
Copyright © 2019 American Chemical Society.
PY - 2019/3/18
Y1 - 2019/3/18
N2 - A pathway to improve the efficiency of Cu2ZnSnS4 (CZTS)-based solar cells, which form an important class of beyond-Si, thin-film photovoltaic technology, is the employment of sustainable isovalent dopants (substituting for Cu and Zn) to suppress formation of disorder-inducing, performance-limiting antisite defects. Using calculations based on density functional theory, we examine the influence of Na and Ca as isovalent dopants for Cu and Zn, respectively, on defect formation, thermodynamic stability, and electronic properties of CZTS. On the basis of defect formation energies, we find that Na-doping should be feasible within CZTS while the incorporation of Ca will be difficult. Importantly, both Na and Ca effectively mitigate formation of antisites that cause disorder, if incorporated within the CZTS structure, across doping and Cu-chemical-potential conditions. Thermodynamically, doping high concentrations of Na into CZTS will result in phase separation between CZTS and Na2ZnSnS4 domains, whereas large additions of Ca will lead to formation of other secondary phases, such as Cu2SnS3 and CaS. With respect to electronic properties, Na (Ca) doping should cause a significant (marginal) increase in the band gap of kesterite CZTS. Overall, we suggest low Na-doping in CZTS as a promising pathway to improve performance of CZTS-based solar cells.
AB - A pathway to improve the efficiency of Cu2ZnSnS4 (CZTS)-based solar cells, which form an important class of beyond-Si, thin-film photovoltaic technology, is the employment of sustainable isovalent dopants (substituting for Cu and Zn) to suppress formation of disorder-inducing, performance-limiting antisite defects. Using calculations based on density functional theory, we examine the influence of Na and Ca as isovalent dopants for Cu and Zn, respectively, on defect formation, thermodynamic stability, and electronic properties of CZTS. On the basis of defect formation energies, we find that Na-doping should be feasible within CZTS while the incorporation of Ca will be difficult. Importantly, both Na and Ca effectively mitigate formation of antisites that cause disorder, if incorporated within the CZTS structure, across doping and Cu-chemical-potential conditions. Thermodynamically, doping high concentrations of Na into CZTS will result in phase separation between CZTS and Na2ZnSnS4 domains, whereas large additions of Ca will lead to formation of other secondary phases, such as Cu2SnS3 and CaS. With respect to electronic properties, Na (Ca) doping should cause a significant (marginal) increase in the band gap of kesterite CZTS. Overall, we suggest low Na-doping in CZTS as a promising pathway to improve performance of CZTS-based solar cells.
KW - CuZnSnS
KW - Defect formation
KW - Density functional theory
KW - Isovalent doping
KW - Solar cells
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U2 - 10.1021/acssuschemeng.8b05348
DO - 10.1021/acssuschemeng.8b05348
M3 - Article
AN - SCOPUS:85062556337
SN - 2168-0485
VL - 7
SP - 5792
EP - 5800
JO - ACS Sustainable Chemistry and Engineering
JF - ACS Sustainable Chemistry and Engineering
IS - 6
ER -