Hostname: page-component-8448b6f56d-xtgtn Total loading time: 0 Render date: 2024-04-25T06:05:54.735Z Has data issue: false hasContentIssue false
  • English
  • Français

Theoretical and experimental investigation of the recombination reduction at surface and grain boundaries in Cu(In,Ga)Se2 solar cells by valence band control

Published online by Cambridge University Press:  30 April 2015

Takahito Nishimura ,
Yoshiaki Hirai ,
Yasuyoshi Kurokawa  and
Akira Yamada
Takahito Nishimura
Affiliation:
Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1-NE-16 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
Yoshiaki Hirai
Affiliation:
Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1-NE-16 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
Yasuyoshi Kurokawa
Affiliation:
Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1-NE-16 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
Akira Yamada
Affiliation:
Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1-NE-16 O-okayama, Meguro-ku, Tokyo 152-8552, Japan Photovoltaics Research Center (PVREC), Tokyo Institute of Technology, 2-12-1-NE-16, O-okayama, Meguro-ku, Tokyo, 152-8552, Japan
Get access

Abstract

We carried out theoretical calculation for Cu(In,Ga)Se2 (CIGS) solar cells with energy bandgap of 1.4 eV assuming formation of a Cu-poor layer on the surface of CIGS films. This calculation result revealed that formation of a thinner Cu-poor layer such as a few nanometers leads to improvement of the solar cells performance. This is because interfacial recombination was suppressed due to repelling holes from the interface by valence band offset (ΔEV). Next, we investigated composition distribution in the cross section of CIGS solar cells with Ga contents of 30% and 70% by transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). It was revealed that the Cu-poor layer was formed on the surface and at the grain boundary (GB) in the case of conversion efficiency (η) of 17.3%, although it was not formed in the case of lower η of 13.8% for a Ga content of 30%. These results indicate that formation of the Cu-poor layer contributed to improvement of cell performance by suppression of carrier recombination. Moreover, it was also confirmed that although the Cu-poor layer was observed on the surface, it was not observed at the GB in the case of CIGS solar cells with a Ga content of 70% which had η of 12.7%. It is thought that the effect of repelling holes by ΔEV is not obtained at the GB and the solar cell performance in the Ga content of 70% is lower than that in the Ga content of 30%. Thus, we suggest importance of the Cu-poor layer at the GB for high efficiency of CIGS solar cells with high Ga contents.

Keywords

compoundmolecular beam epitaxy (MBE)transmission electron microscopy (TEM)
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1771: Symposium B/C/D/E – Recent Advances in Photovoltaics , 2015 , pp. 125 - 131
Copyright
Copyright © Materials Research Society 2015 

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

Powalla, M., Jackson, P., Hariskos, D., Paetel, S., Witte, W., Würz, R., Lotter, E., Menner, R., and Wischemann, W., presented at EU PVSEC29, 2014.Google Scholar
Chirilă, A., Reinhard, P., Pianezzi, F., Bloesch, P., Uhl, A. R., Fella, C., Kranz, L., Keller, D., Gretener, C., Hagendorfer, H., Jaeger, D., Erni, R., Nishiwaki, S., Buecheler, S., and Tiwari, A. N., Nat. Mater 12, 1107 (2013).CrossRefGoogle Scholar
Contreras, M. A., Mansfield, L. M., Egaas, B., Li, J., Romero, M., Noufi, R., Rudiger-voigt, E., and Mannstadt, W., Prog. Photovoltaics Res. Appl 20, 843 (2012).CrossRefGoogle Scholar
Minemoto, T., Matsui, T., Takakura, H., Hamakawa, Y., Negami, T., Hashimoto, Y., Uenoyama, T., and Kitagawa, M., Sol. Energy Mater. Sol. Cells 67, 83 (2001).CrossRefGoogle Scholar
Hirai, Y., Hidaka, Y., Kurokawa, Y., and Yamada, A., Jpn. J. Appl. Phys 51, 10NC03 (2012).CrossRefGoogle Scholar
Heath, J. T., Cohen, J. D., Shafarman, W. N., Liao, D. X., and Rockett, A. A., Appl. Phys. Lett 80, 4540 (2002).CrossRefGoogle Scholar
Schmid, D., Ruckh, M., Grunwald, F., and Schock, H. W., J. Appl. Phys 73, 2902 (1993).CrossRefGoogle Scholar
Schmid, D., Ruckh, M., and Schock, H.W., Sol. Energy Mater. Sol. Cells 41, 281 (1996).CrossRefGoogle Scholar
Hetzer, M. J., Strzhemechny, Y. M., Gao, M., Contreras, M. A., Zunger, A., and Brillson, L. J., Appl. Phys. Lett 86, 162105 (2005).CrossRefGoogle Scholar
Negami, T., Kohara, N., Nishitani, M., Wada, T., and Hirao, T., Appl. Phys. Lett 67, 825 (1995).CrossRefGoogle Scholar
Hirai, Y., Kurokawa, Y., and Yamada, A., Jpn. J. Appl. Phys 53, 012301 (2014).CrossRefGoogle Scholar
Nishimura, T., Hirai, Y., Kurokawa, Y., and Yamada, A., Jpn. J. Appl. Phys (2015) (to be published).Google Scholar
Liu, Y., Sun, Y., and Rockett, A., Sol. Energy Mater. Sol. Cells 98, 124 (2012).CrossRefGoogle Scholar
Azulay, D., Millo, O., Balberg, I., Schock, H.W., Fisher, I. V., and Cahen, D., Sol. Energy Mater. Sol. Cells 91, 85 (2007).CrossRefGoogle Scholar
Taretto, K., Rau, U., and Werner, J. H., Thin Solid Films 480, 8 (2005).CrossRefGoogle Scholar
Persson, C. and Zunger, A., Appl. Phys. Lett 87, 211904 (2005).CrossRefGoogle Scholar