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Temperature Dependence of Electrical Characterization in n+ - CdS/ p - CdTe Thin Film Solar Cells – Study of Shallow/Deep Defects

Published online by Cambridge University Press:  18 January 2013

Poonam Rani Kharangarh ,
George E Georgiou  and
Ken K Chin
Poonam Rani Kharangarh
Affiliation:
Department of Physics and Apollo CdTe Solar Energy Center, New Jersey Institute of Technology (NJIT), University Heights, Newark ,New Jersey, 07102, USA
George E Georgiou
Affiliation:
Department of Physics and Apollo CdTe Solar Energy Center, New Jersey Institute of Technology (NJIT), University Heights, Newark ,New Jersey, 07102, USA
Ken K Chin
Affiliation:
Department of Physics and Apollo CdTe Solar Energy Center, New Jersey Institute of Technology (NJIT), University Heights, Newark ,New Jersey, 07102, USA
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Abstract

For CdTe there is no real distinction between defects and impurities exists when non-shallow dopants are used. These dopants act as beneficial impurities or detrimental carrier trapping centers. Unlike Si, the common assumption that the trap energy level Et is around the middle of the band-gap Ei, is not valid for thin film CdTe. Trap energy levels in CdTe band-gap can distributed with wide range of energy levels above EF. To identify the real role of traps and dopants that limit the solar cell efficiency, a series of samples were investigated in thin film n+-CdS/p-CdTe solar cell, made with evaporated Cu as a primary back contact. It is well known that process temperatures and defect distribution are highly related. This work investigates these shallow level impurities by using temperature dependent current-voltage (I-V-T) and temperature dependent capacitance-voltage (C-V-T) measurements. I-V-T and C-V-T measurements indicate that a large concentration of defects is located in the depletion region. It further suggests that while modest amounts of Cu enhance the cell performance by improving the back contact to CdTe, the high temperature (greater than ∼100°C) process condition degrade device quality and reduce the solar cell efficiency. This is possibly because of the well-established Cu diffusion from the back contact into CdTe. Hence, measurements were performed at lower temperatures (T = 150K to 350K). The observed traps are due to the thermal ionization of impurity centers located in the depletion region of p-CdTe/n+-CdS junction. For our n+-CdS/p-CdTe thin film solar cells, hole traps were observed that are verified by both the measurement techniques. These levels are identical to the observed trap levels by other characterization techniques.

Keywords

defectsphotovoltaicII-VI
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1493: Symposium E/H – Photovoltaic Technologies, Devices and Systems Based on Inorganic Materials, Small Organic Molecules and Hybrids , 2013 , pp. 161 - 167
Copyright
Copyright © Materials Research Society 2013 

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References

REFERENCES

Tan, C. and Xu, M., Solid-State Electron, 32, 25 (1989).CrossRefGoogle Scholar
Li, J. V. and Levi, Dean H., Journal of Applied Physics, 109, p-083701–6 (2011).CrossRefGoogle Scholar
Li, J. V., Yan, Y., Ptak, A. J., Repins, I.L. and Levi, D. H., IEEE Photovoltaic p-000239–000243 (2010).Google Scholar
Mathew, X., Solar Energy Materials & Solar Cells, 70 (2001), 379–393.CrossRefGoogle Scholar
Mathew, X., Solar Energy Materials & Solar Cells, 76 (2003), 225–242.CrossRefGoogle Scholar
Wei, S. H. and Zhang, S. B., Phys. Rev. B. 66 (2002), 155211 CrossRefGoogle Scholar
Anthony, T. C., Fahrenbruch, A.L., and Bube, R.H., J. Vac. Sci. Technol. A2 (1984) 1296.CrossRefGoogle Scholar
Chu, T. L., Chu, S.S., and Ang, S.T., J. Appl. Phys. 64 (1988) 1233.CrossRefGoogle Scholar
McCandless, B.E., Dobson, K.D., Solar Energy 77 (2004) 839.CrossRefGoogle Scholar
Rose, D.H., Hasoon, F.S., Dhere, R.G., Albin, D.S., Ribelin, R.M., Li, X.S., Mahathongdy, Y., Gessert, T.A. and Sheldon, P., Prog. in Photovolt: Res. Appl. 7 331–340(1999).3.0.CO;2-P>CrossRefGoogle Scholar
Kharangarh, P., Misra, D., Georgiou, G. E., and Chin, K. K., “Evaluation of Cu Back Contact Related Deep Defects in CdTe Solar Cells”, ECS Journal of Solid State Science and Technology, 1(5), p. Q110-Q113 (2012).CrossRefGoogle Scholar
Kharangarh, P., Misra, D., Georgiou, G.E., Delahoy, A.E., Cheng, Z., Liu, G., Opyrchal, H., Gessert, T. and Chin, K. K., 38th IEEE PVSC, 2012.Google Scholar
Kharangarh, P., Misra, D., Georgiou, G. E. and Chin, K. K., ECS Transactions, 41(4) p. 233–240 (2011).CrossRefGoogle Scholar
Kushwaha, V. S., Kushwaha, N., Kumar, A., Optoelectronics, J. and Advanced Materials, 8, p. 1814–1816, 2006.Google Scholar
Sze, S. M.. Physics of Semiconductor Devices (2 nd Edition, Wiley 1980).Google Scholar
Rakhshani, A. E., Makdisi, Y., Phys. Status Solidi A, 179(2000), 159.3.0.CO;2-B>CrossRefGoogle Scholar
Castaldini, A., Cavallini, A., Fraboni, B., Appl. Phys. Lett. 69, (1996) 3510.CrossRefGoogle Scholar
Blood, P., Orton, J.W., The Electrical Characterization of Semiconductors: Majority Carriers and Electron States, Academic Press Limited, London0-12-528627-9, 1992.Google Scholar
Seymour, F., Kaydanov, V. and Ohno, T. R., Applied Physics Letter 87, p-153507(1–3) (2005).CrossRefGoogle Scholar
Sah, C. T., Chan, W.W., Fu, H.S., Walker, J.W., Appl. Phys. Lett. 20 (1972) 193.CrossRefGoogle Scholar
Balcioglu, A., Ahrenkiel, R. K., Hasoon, F., J.Appl. Phys. 88 (2000) 7175.CrossRefGoogle Scholar
Versluys, J., Clauws, P., Nollet, P., Degrave, S., Burgelman, M., Thin Solid Films 431–432 (2003) 148.CrossRefGoogle Scholar
Burgelman, M., Nollet, P., Solid State Ionics 176 (2005) 2171.CrossRefGoogle Scholar