Hostname: page-component-cd9895bd7-gvvz8 Total loading time: 0 Render date: 2024-12-23T12:13:41.119Z Has data issue: false hasContentIssue false

Cu2ZnSnS4 thin-film solar cell absorbers illuminated by soft x-rays

Published online by Cambridge University Press:  20 March 2012

M. Bär*
Affiliation:
Solar Energy Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), D-14109 Berlin, Germany; Institut für Physik und Chemie, Brandenburgische Technische Universität Cottbus, D-03046 Cottbus, Germany; and Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, Nevada 89154-4003
B.-A. Schubert
Affiliation:
Solar Energy Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), D-14109 Berlin, Germany
B. Marsen
Affiliation:
Solar Energy Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), D-14109 Berlin, Germany
R.G. Wilks
Affiliation:
Solar Energy Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), D-14109 Berlin, Germany
M. Blum
Affiliation:
Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, Nevada 89154-4003; and Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720
S. Krause
Affiliation:
Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, Nevada 89154-4003
S. Pookpanratana
Affiliation:
Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, Nevada 89154-4003
Y. Zhang
Affiliation:
Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, Nevada 89154-4003; and Department of Physics, Xiamen University, Xiamen 361005, People’s Republic of China
T. Unold
Affiliation:
Solar Energy Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), D-14109 Berlin, Germany
W. Yang
Affiliation:
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720
L. Weinhardt
Affiliation:
Exp. Physik VII, Universität Würzburg, D-97074 Würzburg, Germany
C. Heske
Affiliation:
Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, Nevada 89154-4003
H.-W. Schock
Affiliation:
Solar Energy Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), D-14109 Berlin, Germany
*
a)Address all correspondence to this author. e-mail: [email protected]
Get access

Abstract

In view of the complexity of thin-film solar cells, which are comprised of a multitude of layers, interfaces, surfaces, elements, impurities, etc., it is crucial to characterize and understand the chemical and electronic structure of these components. Because of the high complexity of the Cu2ZnSn(S,Se)4 compound semiconductor absorber material alone, this is particularly true for kesterite-based devices. Hence, this paper reviews our recent progress in the characterization of Cu2ZnSnS4 (CZTS) thin films. It is demonstrated that a combination of different soft x-ray spectroscopies is an extraordinarily powerful method for illuminating the chemical and electronic material characteristics from many different perspectives, ultimately resulting in a comprehensive picture of these properties. The focus of the article will be on secondary impurity phases, electronic structure, native oxidation, and the CZTS surface composition.

Type
Invited Feature Paper
Copyright
Copyright © Materials Research Society 2012

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1.Repins, I., Contreras, M.A., Egaas, B., DeHart, C., Scharf, J., Perkins, C.L., To, B., and Noufi, R.: 19·9%-efficient ZnO/CdS/CuInGaSe2 solar cell with 81·2% fill factor. Prog. Photovoltaics Res. Appl. 16, 235239 (2008).CrossRefGoogle Scholar
2.Jackson, P., Hariskos, D., Lotter, E., Paetel, S., Wuerz, R., Menner, R., Wischmann, W., and Powalla, M.: New world record efficiency for Cu(In, Ga)Se2 thin-film solar cells beyond 20%. Prog. Photovoltaics Res. Appl. 19, 894897 (2011).CrossRefGoogle Scholar
3.Wu, X., Keane, J.C., Dhere, R.G., Dehart, C., Albin, D.S., Duda, A., Gessert, T.A., Asher, S., Levi, D.H., and Sheldon, P.: 16.5%-efficient CdS/CdTe polycrystalline thin-film solar cell. in Proceedings of the Seventeenth European Photovoltaic Solar Energy Conference, edited by McNelis, M.. (Munich, Germany, 2001); pp. 9951000.Google Scholar
4.First Solar, Inc: News releases: “First Solar Announces Second Quarter 2011 Financial Results”, Aug. 8, 2011 and “First Solar Sets World Record for CdTe Solar PV Efficiency”, July 26, 2011. http://investor.firstsolar.com/releases.cfm (accessed August 15, 2011).Google Scholar
5.Green, M.A., Emery, K., Hishikawa, Y., Warta, W., and Dunlop, E.D.: Solar cell efficiency tables (Version 38). Prog. Photovoltaics Res. Appl. 19, 565572 (2011).CrossRefGoogle Scholar
6.Friedlmeier, T.M., Dittrich, H., and Schock, H.-W.: Growth and characterization of Cu2ZnSnS4 and Cu2ZnSnSe4 thin films for photovoltaic applications. Inst. Phys. Conf. Ser. 152A, p. 345 (1998).Google Scholar
7.Tanaka, T., Nagatomo, T., Kawasaki, D., Nishio, M., Guo, Q., Wakahara, A., Yoshida, A., and Ogawa, H.: Preparation of Cu2ZnSnS4 thin films by hybrid sputtering. J. Phys. Chem. Solids 66, 19781981 (2005).CrossRefGoogle Scholar
8.Katagiri, H., Jimbo, K., Yamada, S., Kamimura, T., Maw, W.S., Fukano, T., Ito, T., and Motohiro, T.: Enhanced conversion efficiencies of Cu2ZnSnS4-based thin film solar cells by using preferential etching technique. Appl. Phys. Express 1, 041201 (2008).CrossRefGoogle Scholar
9.Weber, A., Krauth, H., Perlt, S., Schubert, B., Kötschau, I., Schorr, S., and Schock, H-W.: Multistage evaporation of Cu2ZnSnS4 thin films. Thin Solid Films 517, 25242526 (2009).CrossRefGoogle Scholar
10.Scragg, J.J., Berg, D.M., and Dale, P.J.: A 3.2% efficient kesterite device from electrodeposited stacked elemental layers. J. Electroanal. Chem. 646, 5259 (2010).CrossRefGoogle Scholar
11.Babu, G.S., Kumar, Y.K., Bhaskar, P.U., and Raja, V.S.: Effect ofpostdeposition annealing on the growth of Cu2ZnSnSe4 thin films for a solar cell absorber layer. Semicond. Sci. Technol. 23, 085023 (2008).CrossRefGoogle Scholar
12.Babu, G.S., Kumar, Y.K., Bhaskar, P.U., and Raja, V.S.: Effect of Cu/(Zn+Sn) ratio on the properties of coevaporated Cu2ZnSnSe4 thin films. Sol. Energy Mater. Sol. Cells 94, 221226 (2010).CrossRefGoogle Scholar
13.Barkhouse, D.A., Gunawan, O., Gokmen, T., Todorov, T.K., and Mitzi, D.B.: Device characteristics of a 10.1% hydrazine-processed Cu2ZnSn(Se, S)4 solar cell. Prog. Photovoltaics Res. Appl. 20, 611 (2012).CrossRefGoogle Scholar
14.Chen, S., Gong, X.G., Walsh, A., and Wei, S-H.: Crystal and electronic band structure of Cu2ZnSnX4 (X = S and Se) photovoltaic absorbers: First-principles insights. Appl. Phys. Lett. 94, 041903 (2009).CrossRefGoogle Scholar
15.Paier, J., Asahi, R., Nagoya, A., and Kresse, G.: Cu2ZnSnS4 as a potential photovoltaic material: A hybrid Hartree-Fock density functional theory study. Phys. Rev. B 79, 115126 (2009).CrossRefGoogle Scholar
16.Ichimura, M. and Nakashima, Y.: Analysis of atomic and electronic structures of Cu2ZnSnS4 based on first-principle calculation. Jpn. J. Appl. Phys. 48, 090202 (2009).CrossRefGoogle Scholar
17.Persson, C.: Electronic and optical properties of Cu2ZnSnS4 and Cu2ZnSnSe4. J. Appl. Phys. 107, 053710 (2010).CrossRefGoogle Scholar
18.Chen, S., Walsh, A., Yang, J-H., Gong, X.G., Sun, L., Yang, P-X., Chu, J-H., and Wei, S-H.: Compositional dependence of structural and electronic properties of Cu2ZnSn(S, Se)4 alloys for thin film solar cells. Phys. Rev. B 83, 125201 (2011).CrossRefGoogle Scholar
19.Moh, G.H.: Tin-containing mineral systems. Part II: Phase relations and mineral assemblages in the Cu-Fe-Zn-Sn-S system. Chem. Erde 34, 161 (1975).Google Scholar
20.Olekseyuk, I.D., Dudchak, I.V., and Piskach, L.V.: Phase equilibria in the Cu2S–ZnS–SnS2 system. J. Alloys Compd. 368, 135143 (2004).CrossRefGoogle Scholar
21.Schorr, S.: The crystal structure of kesterite type compounds: A neutron and x-ray diffraction study. Sol. Energy Mater. Sol. Cells 95, 14821488 (2011).CrossRefGoogle Scholar
22.Katagiri, H., Ishigaki, N., Ishida, T., and Saito, K.: Characterization of Cu2ZnSnS4 thin films prepared by vapor phase sulfurization. Jpn. J. Appl. Phys. 40, 500504 (2001).CrossRefGoogle Scholar
23.Fernandes, P.A., Salomé, P.M.P., and da Cunha, A.F.: Study of polycrystalline Cu2ZnSnS4 films by Raman scattering. J. Alloys Compd. 509, 76007606 (2011).CrossRefGoogle Scholar
24.Fontané, X., Calvo-Barrio, L., Izquierdo-Roca, V., Saucedo, E., Pérez-Rodriguez, A., Morante, J.R., Berg, D.M., Dale, P.J., and Siebentritt, S.: In-depth resolved Raman scattering analysis for the identification of secondary phases: Characterization of Cu2ZnSnS4 layers for solar cell applications. Appl. Phys. Lett. 98, 181905 (2011).CrossRefGoogle Scholar
25.Abou-Ras, D., Kirchartz, T., and Rau, U.: Advanced Characterization Techniques for Thin Film Solar Cells. (Wiley VCH Verlag GmbH & Co KGaA, Weinheim, Germany, 2011).CrossRefGoogle Scholar
26.Bär, M., Schubert, B-A., Wilks, R.G., Marsen, B., Zhang, Y., Blum, M., Krause, S., Yang, W., Unold, T., Weinhardt, L., Heske, C., and Schock, H-W.: Identification of impurity phases in Cu2ZnSnS4 thin-film solar cell absorber material by soft x-ray absorption spectroscopy, in Compound Semiconductors for Energy Applications and Environmental Sustainability—2011, edited by Bell, L.D., Shahedipour-Sandvik, F., Jones, K.A., Schaadt, D., Simpkins, B.S., and Contreras, M.A. (Mater. Res. Soc. Symp. Proc. 1324, Warrendale, PA, 2011); p. 91, DOI: 10.1557/opl.2011.842.Google Scholar
27.Bär, M., Schubert, B-A., Marsen, B., Schorr, S., Wilks, R.G., Weinhardt, L., Pookpanratana, S., Blum, M., Krause, S., Zhang, Y., Yang, W., Unold, T., Heske, C., and Schock, H-W.: Electronic structure of Cu2ZnSnS4 probed by soft x-ray emission and absorption spectroscopy. Phys. Rev. B 84, 035038 (2011).CrossRefGoogle Scholar
28.Bär, M., Schubert, B-A., Marsen, B., Krause, S., Pookpanratana, S., Unold, T., Weinhardt, L., Heske, C., and Schock, H-W.: Native oxidation and Cu-poor surface structure of thin film Cu2ZnSnS4 solar cell absorbers. Appl. Phys. Lett. 99, 112103 (2011).CrossRefGoogle Scholar
29.Jia, J.J., Callcott, T.A., Yurkas, J., Ellis, A.W., Himpsel, F.J., Samant, M.G., Stoehr, J., Ederer, D.L., Carlisle, J.A., Hudson, E.A., Terminello, L.J., Shuh, D.K., and Perera, R.C.C.: First experimental results from IBM/TENN/TULANE/LLNL/LBL undulator beamline at the advanced light source. Rev. Sci. Instrum. 66, 13941397 (1995).CrossRefGoogle Scholar
30.Schubert, B-A., Marsen, B., Cinque, S., Unold, T., Klenk, R., Schorr, S., and Schock, H-W.: Cu2ZnSnS4 thin film solar cells by fast coevaporation. Prog. Photovoltaics Res. Appl. 19, 9396 (2011).CrossRefGoogle Scholar
31.Schorr, S., Weber, A., Honkimäki, V., and Schock, H-W.: In situ investigation of the kesterite formation from binary and ternary sulphides. Thin Solid Films 517, 2461 (2009).CrossRefGoogle Scholar
32.Meisel, A., Leonhardt, G., and Szargan, R.: X-Ray Spectra and Chemical Binding, Springer Series in Chemical Physics Vol. 37 (Springer, Berlin, 1989).Google Scholar
33.Shishkin, M. and Kresse, G.: Implementation and performance of the frequency-dependent GW method within the PAW framework. Phys. Rev. B 74, 035101 (2006).CrossRefGoogle Scholar
34.Shishkin, M. and Kresse, G.: Self-consistent GW calculations for semiconductors and insulators. Phys. Rev. B 75, 235102 (2007).CrossRefGoogle Scholar
35.Fuchs, F., Furthmüller, J., Bechstedt, F., Shishkin, M., and Kresse, G.: Quasiparticle band structure based on a generalized Kohn-Sham scheme. Phys. Rev. B 76, 115109 (2007).CrossRefGoogle Scholar
36.Hedin, L.: New method for calculating the one-particle green’s function with application to the electron-gas problem. Phys. Rev. 139, A796A823 (1965).CrossRefGoogle Scholar
37.Bär, M., Nishiwaki, S., Weinhardt, L., Pookpanratana, S., Fuchs, O., Blum, M., Yang, W., Denlinger, J.D., Shafarman, W.N., and Heske, C.: Depth-resolved band gap in Cu(In, Ga)(S, Se)2 thin films. Appl. Phys. Lett. 93, 244103 (2008).CrossRefGoogle Scholar
38.Morkel, M., Weinhardt, L., Lohmüller, B., Heske, C., Umbach, E., Riedl, W., Zweigart, S., and Karg, F.: Flat conduction-band alignment at the CdS/CuInSe2 thin-film solar-cell heterojunction. Appl. Phys. Lett. 79, 44824484 (2001).CrossRefGoogle Scholar
39.Weinhardt, L., Morkel, M., Gleim, Th., Zweigart, S., Karg, F., Heske, C., and Umbach, E.: Band alignment at the CdS/CuIn(S, Se)2 heterojunction in thin film solar cells, in Proceedings of the EPVSEC-17, Munich, Germany, October 22–26, 2001, p. 1261.Google Scholar
40.NIST x-ray Photoelectron Spectroscopy Database, Version 3.5 (National Institute of Standards and Technology, Gaithersburg, 2003). http://srdata.nist.gov/xps/ (accessed August 15, 2011).Google Scholar
41.Nanobashvili, E.M., Nemsadze, T.G., and Svanidze, A.S.: Synthesis and properties thiostannates and thiostibites of zinc and cadmium. Soobs. Akad. Nauk. Gruz. SSR 63, 321324 (1971).Google Scholar
42.Tuttle, J.R., Albin, D.S., and Noufi, R.: Thoughts on the microstructure of polycrystalline thin-film CuInSe2 and its impact on material and device performance. Sol. Cells 30, 2138 (1991).CrossRefGoogle Scholar
43.Schmid, D., Ruckh, M., Grunwald, F., and Schock, H-W.: Chalcopyrite/defect chalcopyrite heterojunctions on the basis of CuInSe2. J. Appl. Phys. 73, 29022909 (1993).CrossRefGoogle Scholar
44.Klein, A. and Jaegermann, W.: Fermi-level-dependent defect formation in Cu-chalcopyrite semiconductors. Appl. Phys. Lett. 74, 22832285 (1999).CrossRefGoogle Scholar
45.Schock, H-W. and Rau, U.: The role of structural properties and defects for the performance of Cu-chalcopyrite-based thin-film solar cells. Physica B 308310, 10811085 (2001).CrossRefGoogle Scholar
46.Turcu, M. and Rau, U.: Compositional trends of defect energies, band alignments, and recombination mechanisms in the Cu(In, Ga)(Se, S)2 alloy system. Thin Solid Films 431432, 158162 (2003).CrossRefGoogle Scholar
47.Gunawan, O., Todorov, T.K., and Mitzi, D.B.: Loss mechanisms in hydrazine-processed Cu2ZnSn(Se, S)4 solar cells. Appl. Phys. Lett. 97, 233506 (2010).CrossRefGoogle Scholar
48.Wang, K., Gunawan, O., Todorov, T., Shin, B., Chey, S.J., Bojarczuk, N.A., Mitzi, D., and Guha, S.: Thermally evaporated Cu2ZnSnS4 solar cells. Appl. Phys. Lett. 97, 143508 (2010).CrossRefGoogle Scholar
49.Turcu, M., Pakma, O., and Rau, U.: Interdependence of absorber composition and recombination mechanism in Cu(In, Ga)(Se, S)2 heterojunction solar cells. Appl. Phys. Lett. 80, 25982600 (2002).CrossRefGoogle Scholar
50.Weinhardt, L., Fuchs, O., Blum, M., Bär, M., Weigand, M., Denlinger, J., Zubavichus, Y., Zharnikov, M., Grunze, M., Heske, C., and Umbach, E.: Resonant x-ray emission spectroscopy of liquid water: Novel instrumentation, high resolution, and the “map” approach. J. Electron Spectrosc. Relat. Phenom. 177, 206 (2010).CrossRefGoogle Scholar