Project Title «Horizon 2020»:
NMP-23-2015: Novel materials by design for substituting critical materials

Scientists who are going to participate in the project:
Klochko Natalya P., Senior Staff Scientist, PhD,Materials for electronics and solar cells department (MESC), National Technical University «Kharkiv Polytechnic Institute» (NTU «KhPI»);
Kopach Volodymyr R., Associate Professor, PhD, Materials for electronics and solar cells department (MESC), National Technical University «Kharkiv Polytechnic Institute» (NTU «KhPI»);
Khrypunov Gennady S., Professor, Doctor of Technical Sciences, Head of the Materials for electronics and solar cells department (MESC), National Technical University «Kharkiv Polytechnic Institute» (NTU «KhPI»);

Keywords:
kesterite, tin sulfide, solar cell, electrodeposition, precursor

Abstract:
Thin film solar cells based on polycrystalline copper indium diselenide CuInSe2 (CIS) and copper indium (gallium) diselenide (disulfide) Cu(Ga,In)(S,Se)2 (CIGS) have reached the commercialization stage; however, restrictions on toxic metal usage for Ga and limitations in supply for In and Ga have raised concern about limitations on production capacity of the photovoltaic devices. To solve this issue, it is necessary to develop alternative light absorber materials that are both non-toxic and easily available. In this context, SnS binary semiconductor compound and Cu2ZnSnS4 (CZTS) quaternary semiconductor compound have emerged as promising candidates. We propose new economical technique suitable for the use in mass production to create the base layers tin sulfide (β-SnS) and kesterite Cu2ZnSnS4 by sulfurization of the electrodeposited in standard electrolytes corresponding metal films in sulfur vapor in unsealed reactors suitable for repeated use. Thus the development of advanced effective, cheap and affordable solar cells of a new generation on the base of earth abundant and non-toxic elements be implemented.

Project Idea
The annual growth in the consumption of energy requires expansion of the solar cell market. At the same time, the high cost of manufacturing silicon solar cells predetermines the development of a new generation of photovoltaic devices based on thin semiconductor films. Until recently, chalcopyrite films and, in particular copper indium diselenide CuInSe2 (CIS) and solid solutions Cu(Ga,In)(S,Se)2 (CIGS) based on this compound have been of particular interest as absorbers in thin film solar cells of this kind due to the high absorption coefficient and chemical and physical stability of these materials. Nevertheless, the shortage of indium, high cost of indium and gallium, and toxicity of gallium have initiated the search for alternative photoelectric materials. Solution to these problems consists in using semiconductor compounds such as tin sulfide SnS and kesterite Cu2ZnSnS4 (CZTS), because the abundances of zinc and tin in the Earth’s crust are, respectively, 1500 and 45 times that of indium and the cost of indium is nearly two orders of magnitude that of Zn and Sn. The principal tendency in the development of solar cells based on SnS and CZTS, which will ensure their successful commercialization, consist in the search for an inexpensive high efficiency technique for the fabrication of absorber materials. Because the single stage deposition of the semiconductor compound layers is difficult, two stage processes are advisable: in the first stage, precursors, i.e., films containing only metals are fabricated, and in the second stage, the precursors are transformed into SnS or Cu2ZnSnS4 by means their sulfurization, i.e. by annealing in sulfur vapor. The electrodeposition technique is the best suitable, among other methods, for the fabrication of high quality, inexpensive, and large area precursor films. Electrodeposition has a variety of advantages, including low process costs, high efficiency, high deposition rate, and no requirements for the use of toxic gases. Sulfurization of the precursors for the obtaining SnS and Cu2ZnSnS4 will be performed in unsealed reactors suitable for repeated use.

A list of organizations that are ready to join the project (if any)
N. Zhukovsky National Aerospace University “Kharkiv Aviation Institute”; Ukraine and National Taras Shevchenko University, Kyiv, Ukraine are already involved.

Scientific novelty:
An economical technique suitable for use in mass production is presented for producing of orthorhombic herzenbergite type tin sulfide (β-SnS) layers and kesterite Cu2ZnSnS4 layers obtained by sulfurization of the electrodeposited in standard electrolytes corresponding metal films in sulfur vapor in unsealed reactors suitable for repeated use. The selection of the optimal sequence of the alternating of copper, tin and zinc films in the precursors, atomic ratios of the electrodeposited precursor components and sulfur, and the sulfurization modes have provided syntheses of single phase kesterite and tin sulfide layers. The synthesized polycrystalline semiconductor SnS and Cu2ZnSnS4 layers are characterized by structure and optical properties optimal for solar energy harvesting and so they are promising for use as base layers for advanced effective, cheap and affordable tin sulfide and kesterite thin film solar cells of a new generation on the base of earth abundant and non-toxic elements.

List of the most significant publications in the international journals included in the Scopus database (if any):
1. E. I. Sokol, I.I. Tyukhov, N.P. Klochko, G.S. Khrypunov, Y.O. Myagchenko, E.E. Melnychuk, V.R. Kopach, O.V. Momotenko, K.S. Klepikova, V.M. Lyubov, A.V. Kopach. Pulse plating of semiconductors for solar cells // // Solar Energy, 2014, V. 105, July, рр. 373–380.
2. Klochko N.P., Khrypunov G.S., Volkova N.D., Kopach V.R., Momotenko A.V., Lubov V.N. Structure and properties of electrodeposited films and film stacks for precursors of chalcopyrite and kesterite solar cells // Semiconductors – 2014. – V. 48. – №4. – P. 521- 530.

Expected results:
New economical technique suitable for the use in mass production to create the base layers for advanced effective, cheap and affordable solar cells of a new generation on the base of earth abundant and non-toxic elements.

Contacts:
Klochko Natalya, Senior Staff Scientist, PhD, Materials for electronics and solar cells department (MESC), National Technical University “Kharkiv Polytechnic Institute”, 21, Frunze str., 61002 Kharkiv, Ukraine
Correspondent Address 61070, Acad. Proskura str., 10, Apt.8, Kharkiv, Ukraine
Email: klochko_np@mail.ru
Phone: +380973916406