Effect of Annealing Temperature and Ambient on Formation, Composition and Bandgap of Cu2ZnSnS4 Thin Films
Y.M. Suna,b,c, B. Yaoa,b, X.C. Meng c, D. Wang c, D. Long c, Z. Hua c
aState Key Lab of Superhard Material and College of Physics, Jilin University, Changchun 130023, P.R. China
bKey Laboratory of Physics and Technology for Advanced Batteries of Ministry of Education, College of Physics, Jilin University, Changchun, 130012, China
cKey Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, P.R. China
Received: January 29, 2014; In final form: April 18, 2014
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Amorphous Cu-Zn-Sn-S precursor films were prepared by sol-gel and spin-coating with copper chloride, zinc chloride, tin chloride and thiourea solutions as starting materials. A Cu2ZnSnS4 film with kesterite structure and a small amount of chlorine formed when the precursor was annealed under Ar ambient at temperature above 200°C, but its atomic ratios of Cu:Zn:Sn:S far deviated from stoichiometric ratios of the Cu2ZnSnS4. However, when the precursor films were annealed with sulfur powder together at temperatures between 360 and 480°C, the CZTS film containing a very small amount of Cl formed, and its atomic ratio change little for Cu, Zn, and Sn, increases for S and decreases for Cl with increasing temperature. When the temperature is 480°C, a CZTS only has Cu, Zn, Sn, and S element is fabricated, and the atomic ratio of Cu:Zn:Sn:S is near the stoichiometric ratio. The bandgap of the CZTS decreases with increasing annealing temperature. The mechanisms of the formation and the properties of the CZTS are suggested in the present work.

DOI: 10.12693/APhysPolA.126.751
PACS numbers: 68.55.-a