Hostname: page-component-7c8c6479df-hgkh8 Total loading time: 0 Render date: 2024-03-28T13:02:11.879Z Has data issue: false hasContentIssue false

Defect Densities, Diffusion Lengths and Device Physics in Nanocrystalline Si:H Solar Cells

Published online by Cambridge University Press:  21 March 2011

Vikram L. Dalal
Affiliation:
Iowa State University, Dept. of Electrical and Computer Engr. and Microelectronics Research Center, Ames, Iowa 50011, USA
Puneet Sharma
Affiliation:
Iowa State University, Dept. of Electrical and Computer Engr. and Microelectronics Research Center, Ames, Iowa 50011, USA
Max Noack
Affiliation:
Iowa State University, Microelectronics Research Center, Ames, Iowa 50011,USA
Keqin Han
Affiliation:
Iowa State University, Microelectronics Research Center, Ames, Iowa 50011,USA
Get access

Abstract

We report on the properties of nanocrystalline Si:H solar cells. The solar cells were of the p+nn+ type, with the n+ layer deposited first on a stainless steel substrates. The solar cells were prepared under high hydrogen dilution conditions using either ECR plasma deposition, or VHF diode plasma deposition processes. The deposition pressures were kept low, 5 mTorr in the ECR reactor and 50 mTorr in the VHF reactor. All the solar cells reported showed a high Raman ratio of crystalline to amorphous peaks. Properties such as dark current, deep level defects and shallow doping densities, and hole diffusion lengths were measured in these cells. It was found that the base layer was always n type, but that its doping could be changed by adding ppm levels of B during growth. A sufficient B doping even type converted the base layer to p type. It was found that there was a good one-to-one correlation between the shallow doping and deep level defects, suggesting that the same element, probably oxygen, is responsible for generating both shallow dopants and deep levels. The diffusion length of holes was measured in these cells using quantum efficiency vs. voltage techniques, and it was found that the diffusion length data could be explained very well by invoking trap-controlled recombination statistics. The dark I(V) curves could be represented by a standard diode model for highly crystalline materials, but as the degree of crystallinity was reduced, the diode factor increased. Voltage could be improved by reducing the crystallinity of the layer, but doing so resulted in a decrease in quantum efficiency in the infrared regions of the solar spectrum.

Type
Research Article
Copyright
Copyright © Materials Research Society 2004

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. Yamamoto, Kenji, Yoshimi, Masashi, Tawada, Yuko, Fukuda, Susumu, Sawada, Toru, Meguro, Tomomi, Takata, Hiroki, Suezaki, Takashi, Koi, Yohei, Hayashi, Katsuhiko Solar Energy Mater. And Solar Cells, 74, 449455 (2002)Google Scholar
2. Rech, B., Kluth, O., Repmann, T., Roschek, T., Springer, J., Müller, J., Finger, F., Stiebig, H. and Wagner, H., Solar Energy Mater. And Solar Cells, 74, 439447(2002)Google Scholar
3. Meier, J., Dubail, S., Golay, S., Kroll, U., Fa, S., Vallat-Sauvain, E., Feitknecht, L., Dubail, J. and Shah, A., Solar Energy Mater. And Solar Cells, 74, 457467(2002)Google Scholar
4. Shah, A. V., Meier, J., Vallat-Sauvain, E., Wyrsch, N., Kroll, U., Droz, C. and Graf, U., Solar Energy Mater. And Solar cells, 78, Pages 469491 (2003)Google Scholar
5. Dalal, V. L., Zhu, Jianhua, Noack, Max and Welsh, Matt, IEE Proc.-Circuits and Devices, 150, 316(2003)Google Scholar
6. Biswas, R. and Pan, B. C., Proc. Of Mater. Res. Soc., 762, 15 (2003)Google Scholar
7. Dalal, V. L. and Erickson, K., Proc. Of Mater.Res.Soc, Vol. 609(2000)Google Scholar
8. Kimerling, L. C., Journal of Applied Physics, v 45, p 18391845 (1974)Google Scholar
9. Lips, K., Kanshat, P., Fuhs, W., Solar Energy Mater. and Solar Cells, v 78, p 513541(2003)Google Scholar
10.See, for example, Streetman, B. and Banerjee, S., “Solid State Electronic Devices”, 5th. Ed., (Prentice Hall,NY, 2000), p. 380 Google Scholar