In order to investigate the influence of parasitic resistances, saturation current and diode ideality factor on the performance of photovoltaic devices, parameter extraction routines employing the standard iteration (SI) method and the particle swarm optimization (PSO) method were developed to extract the series resistance, shunt resistance, saturation current and ideality factor from the I-V characteristics of solar cells and PV modules. The well-known one- and two-diode models were used to describe the behavior of the I-V curve and the parameters of the models were determined by approximation and iteration techniques. The SI and the PSO extraction programmes were used to assess the suitability of the one- and the two-diode solar cell models in describing the I-V characteristics of mono- and multicrystalline silicon solar cells, CISS- and CIGSS-based solar cells. This exercise revealed that the two-diode model provides more information regarding the different processes involved in solar cell operation. Between the two methods developed, the PSO method is faster, yielded fitted curves with lower standard deviation of residuals and, therefore, was the preferred extraction method. The PSO method was then used to extract the device parameters of CISS-based solar cells with the CISS layer selenized under different selenization process conditions and CIGSS-based solar cells with varying i-ZnO layer thickness. For the CISS-based solar cells, the detrimental effect of parasitic resistances on device performance increased when the temperature and duration of the selenization process was increased. For the CIGSS-based devices, photogeneration improved with increasing i-ZnO layer thickness. At high forward bias, bulk recombination and/or tunneling-assisted recombination were the dominant processes affecting the I-V characteristics of the devices. v Lastly, device and performance parameters of mono-, multicrystalline silicon and CIS modules derived from I-V characteristics obtained under dark and illuminated conditions were analyzed considering the effects of temperature on the performance of the devices. Results showed that the effects of parasitic resistances are greater under illumination and, under outdoor conditions, the values further declined due to increasing temperature. The saturation current and ideality factor also increased under outdoor conditions which suggest increased recombination and, coupled with the adverse effects of parasitic resistances, these factors result in lower FF and lower maximum power point. Analysis performed on crystalline silicon and thin film devices utilized in this study revealed that parameter extraction from I-V characteristics of photovoltaic devices and, in particular, the implementation of PSO in solar cell device parameter extraction developed in this work is a useful characterization technique.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nmmu/vital:10538 |
| Date | January 2009 |
| Creators | Macabebe, Erees Queen Barrido |
| Publisher | Nelson Mandela Metropolitan University, Faculty of Science |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis, Doctoral, PhD |
| Format | ix, 114 leaves, pdf |
| Rights | Nelson Mandela Metropolitan University |
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