Power Conversion Enhancement of CdS/CdTe Solar Cell Interconnected with Tunnel Diode


One of the most promising solar cell devices is cadmium telluride (CdTe) based. These cells however, have their own problems of stability and degradation in efficiency. Measurements show that CdS/CdTe solar cell has high series resistance which degrades the performance of solar cell energy conversion. Both active layers (CdS and CdTe) had been fabricated by thermal evaporation and tested individually. It was found that CdS window layer of 300 nm have the lowest series resistance with maximum light absorption. While 5 - 7 μm CdTe absorber layer absorbed more than 90% of the incident light with minimum series resistance. A complete CdS/CdTe solar cell was fabricated and tested. It was found that deposited cell without heat treatment shows that the short circuit current increment decreases as the light intensity increases. This type of deposited cell has low conversion efficiency. The energy conversion efficiency was improved by heat treatment, depositing heavily doped layer at the back of the cell and minimizing the contact resistivity by depositing material with resistivity less than 1 m??cm2. All these modifications were not enough because the back contact is non-ohmic. Tunnel diode of CdTe (p++)/CdS (n++) was deposited in the back of the cell. The energy conversion efficiency was improved by more than 7%.

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W. Mohammed, O. Daoud and M. Al-Tikriti, "Power Conversion Enhancement of CdS/CdTe Solar Cell Interconnected with Tunnel Diode," Circuits and Systems, Vol. 3 No. 3, 2012, pp. 230-237. doi: 10.4236/cs.2012.33032.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] X. Wu, J. C. Keane, R. G. Dhere, C. DeHart, A. Duda, T. A. Gessert, S. Asher, D. H. Levi and Sheldon, “16.5% Efficient CdS/CdTe Polycrystalline Thin-Film Solar Cell,” Proceedings of the 17th E-PVSEC, München, October 2001, pp. 995-1000.
[2] D. Cunningham, K. Davies, L. Grammond, E. Mopas, M. O’Connor, M. Rubcich, M. Sadeghi, D. Skinner and T. Trumbly, “Large Area Apollo Module Performance and Reliability,” Proceedings of the 28th IEEE Photovoltaic Specialists Conference, Fairfield, 2000, pp. 13-18. doi:10.1109/PVSC.2000.915743
[3] S. Sze, “Physics of semiconductor Devices,” 2nd Edition, Wiley, New York, 1981.
[4] R. Birkmire, “CdTe1–xSx Absorber Layers for Thin-Film CdTe/CdS Solar Cells,” 26th IEEE Photovoltaic’s Specialists Conference (PVSC), Anaheim, Vol. 295, 1997, pp. 307-312.
[5] M. V. Garcia-Cuenc, J. L. Morenza, E. Bertran and A. Lousa, “Electrical Conduction in Polycrystalline CdS Films: Comparison of Theory and Experiment,” Journal of Physics D: Applied Physics, Vol. 20, No. 7, 1987, pp. 958-962. doi:10.1088/0022-3727/20/7/020
[6] A. Sanchez, P. J. Sebastian and O. Gomez-Daza, “LowResistivity CdS Thin Films Formed by a New Chemical Vapor Transport Method,” Semiconductor Science and Technology, Vol. 10, No. 1, 1995, pp. 87-90. doi:10.1088/0268-1242/10/1/014
[7] W. F. Mohammed, “The Effect of Temperatures and Doped Level on CdS Thin Films,” Engineering & Technology Journal, Vol. 14, No. 7, 1995, p. 34.
[8] W. F. Mohammed and M. A. Shehathah, “Effect of Series Resistance on Photovoltaic Properties of In-Doped CdTe (p) Thin Film Homojunction Structure,” Renewable Energy, Vol. 21, No. 3, 2000, pp. 141-152. doi:10.1016/S0960-1481(00)00008-2
[9] F. Zhou, X. C. Wang, H. C. Wu and C. Z. Zhao, “Achievements and Challenges of CdS/CdTe Solar Cells,” International Journal of Photo Energy, Vol. 2011, 2011, pp. 1-8.
[10] W. F. Mohammed and M. A. Shehathah, “The Electrical Properties of Post-Deposition Annealed and As-Deposited In-Doped CdTe Thin Films,” Renewable Energy, Vol. 26, 2002, pp. 285-249. doi:10.1016/S0960-1481(00)00195-6
[11] M. M. Al-Jassim, R. G. Dhere, K. M. Jons, F. S. Hasoon and Sheldon, “The Morphology, Microstructure, and Luminescent Properties of CdS/CdTe Films,” 2nd World Conference and Exhibition on Photovoltaic Solar Energy Conversion, Vienna, 6-10 July 1998.
[12] D. H. Levi, L. M. Woods, D. S. Albin and T. A. Gessert, “The Influence of Grain Boundary Diffusion on the Electro-Optical Properties of CdTe/CdS Solar Cells,” 2nd World Conference and Exhibition on Photovoltaic Solar Energy Conversion, Vienna, 6-10 July 1998.
[13] G. Khrypunov, A. Romeo, F. Kurdesau, D. L. Batnzer, H. Zogg and D. L. Tiwari, “Recent Development in Evaporated CdTe Solar Cells,” Solar Energy Material and Solar Cells, Vol. 90, No. 6, 2006, p. 664. doi:10.1016/j.solmat.2005.04.003
[14] S. Hegedus, D. Desai and C. Thompson, “Voltage Dependent Photocurrent Collection in CdTe/CdS Solar Cells,” Progress Photovoltaic: Research and Applications, Vol. 15, No. 7, 2007, p. 587. doi:10.1002/pip.767
[15] Y. J. Li, et al., “Preparation and Performance of CdS/ CdTe Tandem Solar Cells,” Chinese Journal of Semiconductors, Vol. 5, 2007, pp. 722-725.
[16] X. Mathew, J. Drayton, V. Parikh, N. R. Mathews, X. X. Liu and A. D. Compaan, “Development of a Semitransparent CdMgTe/CdS Top Cell for Applications in Tandem Solar Cells,” Semiconductor Science Technology, Vol. 24, No. 1, 2009, Article ID 015012. doi:10.1088/0268-1242/24/1/015012
[17] W. F. Mohammed and A. Nori, “The Photo-Electric and Thermal Properties of Vacuum Deposited CdS Thin Films,” Renewable Energy Journal, Vol. 14, No. 1-4, 1998, pp. 129-134. doi:10.1016/S0960-1481(98)00058-5
[18] W. F. Mohammed and A. Nori, “The Effect of Deposition Parameters on Hall Mobility and Carrier Concentration of CdS Thin Films,” Abhath Al-Yarmook Journal, Vol. 11, No. 1B, 2002, pp. 402-412.
[19] H. A. Ahmed and L. S. Ali, “Characterization of In-Doped CdTe Thin Film,” Muutah Journal for Research and Studies, Vol. 11, No. 5, 1996, pp. 207-218.
[20] W. Guter, F. Dimroth, M. Meusel and A. W. Bett, “Tunnel Diodes for III-V Multi-Junction Solar Cells,” 20th European Photovoltaic Solar Energy Conference, Barcelona, June 2005, pp. 515-518.
[21] L. Kosyachenko, “Efficiency of Thin-Film CdS/CdTe Solar Cells,” In: R. D. Rugescu, Ed., Solar Energy, 2010, pp. 105-130. doi:10.5772/8065
[22] M. Wolf and H. Rauschenbusch, “Series resistance Effects on Solar Cell Measurements,” Advanced Energy Conversion, Vol. 3, 1963, pp. 455-479. doi:10.1016/0365-1789(63)90063-8
[23] A. W. Brinkman and S. M. Al-Amri, “Thin Film CdTe Based Solar Cell,” Proceedings of the 6th Arab International Solar Energy Conference, Muscat, 1998.
[24] J. Sites and J. Pan, “Strategies to Increase CdTe SolarCell Voltage,” Thin Solid Films, Vol. 515, No. 15, 2007, pp. 6099-6102. doi:10.1016/j.tsf.2006.12.147
[25] N. Amin, K. Sopian and M. Konagai, “Numerical Modeling of CdS/CdTe and CdS/CdTe/ZnTe Solar Cells as a Function of CdTe Thickness,” Solar Energy Materials and Solar Cells, Vol. 91, No. 13, 2007, pp. 1202-1208. doi:10.1016/j.solmat.2007.04.006
[26] W. Guter and A. W. Bett, “I-V Characterization of Tunnel Diodes and Multijunction Solar Cells,” IEEE Transactions on Electron Devices, Vol. 53, No. 9, 2006, pp. 2216-2222. doi:10.1109/TED.2006.881051

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