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International Journal of Photoenergy
Volume 2017 (2017), Article ID 8479487, 9 pages
https://doi.org/10.1155/2017/8479487
Research Article

Extraction of Saturation Current and Ideality Factor from Measuring Voc and Isc of Photovoltaic Modules

University of Fort Hare, Institute of Technology, Private Bag X1314, Alice 5700, South Africa

Correspondence should be addressed to E. L. Meyer; az.ca.hfu@reyeme

Received 17 June 2017; Revised 7 September 2017; Accepted 27 September 2017; Published 19 December 2017

Academic Editor: K. R. Justin Thomas

Copyright © 2017 E. L. Meyer. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Saturation current (I0) and ideality factor (n) of a p-n junction solar cell are an indication of the quality of the cell. These two parameters are usually estimated from dark current-voltage measurements. In this study, a quick and easy method to determine these two parameters by measuring open-circuit, Voc, and short-circuit current, Isc, is presented. Solar cell designers can use this method as a grading or diagnostic tool to evaluate degradation in photovoltaic (PV) modules. In order to verify the Voc-Isc method, a series of experiments have been conducted on a single cell and a 36-cell module. Good agreement between our Voc-Isc method and dark I-V measurements was obtained. An application of the method on the performance degradation of a single-junction a-Si:H module revealed that the module’s I0 increased by more than three orders of magnitude and n increased by 65% after an outdoor exposure of 130 kWh/m2. This increase in n indicates that after exposure, the recombination current in the cells’ space charge region increased due to the light-induced formation of metastable defects. The method is also used to assess the quality of five PV module technologies and proved to be reliable despite defective cells in a module.