Hostname: page-component-76fb5796d-wq484 Total loading time: 0 Render date: 2024-04-27T01:38:02.283Z Has data issue: false hasContentIssue false
  • English
  • Français

Microcrystalline Silicon for Solar Cells at High Deposition Rates by Hot Wire Cvd

Published online by Cambridge University Press:  01 February 2011

R. E. I. Schropp ,
Y. Xu ,
E. Iwaniczko ,
G. A. Zaharias  and
A. H. Mahan
R. E. I. Schropp
Affiliation:
Utrecht University, Debye Institute, Physics of Devices, 3508 TA Utrecht, The Netherlands
Y. Xu
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401, USA
E. Iwaniczko
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401, USA
G. A. Zaharias
Affiliation:
Chem. Engineering Dept., Stanford University, Stanford, CA 94305, USA
A. H. Mahan
Affiliation:
National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401, USA
Get access

Abstract

We have explored which deposition parameters in Hot Wire CVD have the largest impact on the quality of microcrystalline silicon (μc-Si) made at deposition rates (Rd) < 10 Å/s for use in thin film solar cells. Among all parameters, the filament temperature (Tfil) appears to be crucial for making device quality films. Using two filaments and a filament-substrate spacing of 3.2 cm, μc-Si films, using seed layers, can be deposited at high Tfil (∼2000°C) with a crystalline volume fraction < 70-80 % at Rd's < 30 Å/s. Although the photoresponse of these layers is high (< 100), they appear not to be suitable for incorporation into solar cells, due to their porous nature. n-i-p cells fabricated on stainless steel with these i-layers suffer from large resistive effects or barriers, most likely due to the oxidation of interconnected pores in the silicon layer. The porosity is evident from FTIR measurements showing a large oxygen concentration at ∼1050 cm-1, and is correlated with the 2100 cm-1 signature of most of the Si-H stretching bonds. Using a Tfil of 1750°C, however, the films are more compact, as seen from the absence of the 2100 cm-1 SiH mode and the disappearance of the FTIR Si-O signal, while the high crystalline volume fraction (< 70-80 %) is maintained. Using this Tfil and a substrate temperature of 400°C, we obtain an efficiency of 4.9 % for cells with a Ag/ZnO back reflector, with an i-layer thickness of only ∼0.7 μm. High values for the quantum efficiency extend to very long wavelengths, with values of 33 % at 800 nm and 15 % at 900 nm, which are unequalled by a-SiGe:H alloys. Further, by varying the substrate temperature to enable deposition near the microcrystalline to amorphous transition (‘edge’) and incorporating variations in H2 dilution during deposition of the bulk, efficiencies of 6.0 % have been obtained. The Rd's of these i-layers are 8-10 Å/s, and are the highest to date obtained with HWCVD for microcrystalline layers used in cells with efficiencies of ∼6 %.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 715: Symposium A – Amorphous and Heterogeneous Silicon-Based Films-2002 , 2002 , A26.3
Copyright
Copyright © Materials Research Society 2002

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

[1] Yamamoto, K., Yoshimi, M., Tawada, Y., Okamoto, Y., Nakajima, A., Igari, S., Appl. Phys. A 69 (1999) 179.Google Scholar
[2] Meier, J., Torres, P., Platz, R., Dubail, S., Kroll, U., Anna, J.A. Selvan, Pellaton Vaucher, N., Hof, Ch., Fischer, D., Keppner, H., Shah, A., Ufert, K.D., Giannoules, P., and Koehler, J., MRS Symp. Proc. 420, 3(1996).Google Scholar
[3] Klein, S., Finger, F., Carius, R., Kluth, O., Baia Neto, L., Wagner, H., Stutzmann, M., 17th European Photovoltaic Conference and Exhibition, München, 22–26 October (2001), in press.Google Scholar
[4] Jones, S.J., Crucet, R., Deng, X., Williamson, D.L., and Izu, M., MRS Symp. Proc. 609, A4.5 (2000).Google Scholar
[5] Morrison, S., K, U.. Das, and Madan, A., NREL Report EL-520-31065, 179 (2001).Google Scholar
[6] Mahan, A.H., Xu, Y., Williamson, D.L., Beyer, W., Perkins, J.D., Vanecek, M., Gedvilas, L.M., and Nelson, B.P., J. Appl. Phys. 90, 5038(2001).Google Scholar
[7] Mahan, A.H., Xu, Y., Iwaniczko, E., Williamson, D.L., Nelson, B.P., and Wang, Q., J. non-Cryst. Sol., April (2002), in press.Google Scholar
[8] Nelson, B.P., Xu, Y., Mahan, A.H., Williamson, D.L., and Crandall, R.S., MRS Symp. Proc. 609, A22.8 (2000).Google Scholar
[9] Wang, Q., Iwaniczko, E., Xu, Y., Gao, W., Nelson, B.P., Mahan, A.H., Crandall, R.S., and Branz, H.M., MRS Symp. Proc. 609, A4.3 (2000).Google Scholar
[10] Zaharias, G. et al., these proceedingsGoogle Scholar
[11] See Fig. 1 in Mahan, A.H., Williamson, D.L., and Furtak, T.E., MRS Symp. Proc. 467, 657(1997).Google Scholar
[12] Schropp, R.E.I., Alkemade, P.F.A., and Rath, J.K., Solar Energy Materials & Solar Cells 65 (2000) 541.Google Scholar
13] Schropp, R.E.I. and Zeman, M., Amorphous and Microcrystalline Silicon Solar Cells: Modeling, Materials, and Device Technology, Kluwer Academic Publishers, ISBN 0-7923-8317-6 (Boston/Dordrecht/London, 1998).Google Scholar
[14] Rath, J.K., Meiling, H., and Schropp, R.E.I., Solar Energy Materials and Solar Cells 48 (1997) 269.Google Scholar
[15] See, for example, the proceedings of the 12th Int'l Photovoltaic Science and Engineering Conference, Jeju, Korea, 11-15 June (2001), and references therein.Google Scholar