Investigation of the Current-Voltage Characteristics of CdS/CdTe-Based Solar Cells Using Model Calculations
CdTe can be grown as n-type or p-type although the p-type can also be formed by converting n-CdTe to p-CdTe through the well known CdCl2 treatment, which is an important step taken to improve the conversion efficiency of CdTe solar cells. However, the assumption by most researchers is that CdTe is always a p-type material and so can only form a p-n junction with its n-CdS counterpart. This is not always the case as n-n heterojunction + Schottky junction can be formed when an n-CdTe is involved, with group I metals such as Au and Cu as back metal contact. In this work, p-n junction model and Schottky junction model are presented. In order to verify the junction type formed by various CdS/CdTe-based solar cells reported in the literature, current-voltage data of these experimental results are simulated with the junction models using MATLAB programming platform and compared so as to find out the junction model that best describes each experimental result. Diode parameters such as ideality factor, barrier height, and series resistance were adjusted during the simulation. The junction models are found to be in good agreement with some of the experimental results.
S. Babkair, "Charge Transport Mechanisms and Device Parameters of CdS/CdTe Solar Cells Fabricated by Thermal Evaporation," J. King Abdulaziz Univ., vol. 22, no. 1, pp. 21–33, 2010.
M. Wimbor, A. Romeo, and M. Igalson, "Electrical characterisation of CdTe/CdS photovoltaic devices," Opto-Electronics Rev., vol. 8, no. 4, pp. 375–377, 2000.
X. Wu, "High-Efficiency Polycrystalline CdTe Thin-Film Solar Cells," Solar Energy, vol.77, no. 6, pp. 803-814, 2004.
I.M. Dharmadasa, “Review of the CdCl2 Treatment Used in CdS/CdTe Thin Film Solar Cell Development and New Evidence towards Improved Understanding,” Coatings, vol. 4, no. 2, pp. 282–307, 2014.
O.K. Echendu, F. Fauzi, A. R. Weerasinghe, and I. M. Dharmadasa, "High Short-Circuit Current Density CdTe Solar Cells Using All-Electrodeposited Semiconductors," Thin Solid Films, vol. 556, pp. 529–534, 2014.
T. Schulmeyer, J. Fritsche, A. Thißen, A. Klein, W. Jaegermann, M. Campo, J. Beier, “Effect of In Situ UHV CdCl2-Activation on the Electronic Properties of CdTe Thin Film Solar Cells,” Thin Solid Films, vol. 431-432, pp. 84-89, 2003.
I.M. Dharmadasa, P.A. Bingham, O.K. Echendu, H.I. Salim, T. Druffel, R. Dharmadasa, G.U. Sumanasekera, R.R. Dharmasena, M.B. Dergacheva, K.A. Mit, K.A. Urazov, L. Bowen, M. Walls, A. Abbas, “Fabrication of CdS/CdTe Based Thin Film Solar Cells Using an Electrochemical Technique,” Coatings, vol. 4, pp. 380-415, 2014.
C. Li, Y. Wu, J. Poplawsky, T.J. Pennycook, N. Paudel, W. Yin, S.J. Haigh, M.P. Oxley, A.R. Lupini, M. Al-Jassim, S.J. Pennycook, Y. Yan, “Grain-boundary enhanced carrier collection in CdTe solar cells,” Phys. Rev. Lett., vol. 112, no. 15, 2014.
O.K. Echendu and I.M. Dharmadasa, “The Effect on CdS/CdTe Solar Cell Conversion Efficiency of the Presence of Fluorine in the Usual CdCl2 Treatment of CdTe,” Materials Chemistry and Physics, vol. 157, pp. 39-44, 2015.
S.M. Sze and K.K. Ng, “Physics of Semiconductor Devices,” 3rd edition, John Wiley & Sons, Inc., New Jersey, United States of America, 2007.
T. Soga, “Nanostructured Materials for Solar Energy Conversion,” Chapter1, Edited by Tetsu Soga and Published by Elsevier, 2006.
D. Cahen, K. Gartsman, G. Hodes, O. Rotlevy, I. Visoly-Fisher, & K. Dobson, “Overcoming Degradation Mechanisms in CdTe Solar Cells,” 2000. Retrieved July 18, 2017 from https://digital.library.unt.edu/ark:/67531/metadc710520/m2/1/high_res_d/754634.pdf
L. Wu, L. Feng, W. Li, J. Zhang, B. Li, Z. Lei, … J. Zheng, “Effect of ZnTe/ZnTe:Cu Complex Back-Contact on Device Characteristics of CdTe Solar Cells”. Science in China, Series E: Technological Sciences, vol. 50, no. 2, pp. 199–205, 2007.
G. Luo, B. Lv, W. Li, L. Feng, J. Zhang, L. Wu, & G. Zeng, “Characterization of Cu1.4Te Thin Films for CdTe Solar Cells”. International Journal of Photoenergy, vol. 2014, Article ID 762576, 5 pages, 2014.
O.K. Echendu & I.M. Dharmadasa, “Graded-Bandgap Solar Cells Using All-Electrodeposited ZnS, CdS and CdTe Thin-Films”. Energies, vol. 8, no. 5, pp. 4416–4435, 2015.
Copyright (c) 2019 Adaeze Erinma Nwogwugwu, Obi Kingsley Echendu, Bede Chinyere Anusionwu
This work is licensed under a Creative Commons Attribution 4.0 International License.
The author warrants that the article is original, written by stated author(s), has not been published before, contains no unlawful statements, does not infringe the rights of others, is subject to copyright that is vested exclusively in the author and free of any third party rights, and that any necessary written permissions to quote from other sources have been obtained by the author(s).