Device and performance parameters of Cu(In,Ga)(Se,S)2-based solar cells with varying i-ZnO layer thickness
Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth, 6031, South Africa; Department of Physics, University of Johannesburg, P.O. Box 524, Auckland Park, 2006, South Africa
Macabebe, E.Q.B., Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth, 6031, South Africa; Sheppard, C.J., Department of Physics, University of Johannesburg, P.O. Box 524, Auckland Park, 2006, South Africa; van Dyk, E.E., Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth, 6031, South Africa
In pursuit of low-cost and highly efficient thin film solar cells, Cu(In,Ga)(Se,S)2/CdS/i-ZnO/ZnO:Al (CIGSS) solar cells were fabricated using a two-step process. The thickness of i-ZnO layer was varied from 0 to 454 nm. The current density-voltage (J-V) characteristics of the devices were measured, and the device and performance parameters of the solar cells were obtained from the J-V curves to analyze the effect of varying i-ZnO layer thickness. The device parameters were determined using a parameter extraction method that utilized particle swarm optimization. The method is a curve-fitting routine that employed the two-diode model. The J-V curves of the solar cells were fitted with the model and the parameters were determined. Results show that as the thickness of i-ZnO was increased, the average efficiency and the fill factor (FF) of the solar cells increase. Device parameters reveal that although the series resistance increased with thicker i-ZnO layer, the solar cells absorbed more photons resulting in higher short-circuit current density (Jsc) and, consequently, higher photo-generated current density (JL). For solar cells with 303-454 nm-thick i-ZnO layer, the best devices achieved efficiency between 15.24% and 15.73% and the fill factor varied between 0.65 and 0.67. © 2009 Elsevier B.V. All rights reserved.
Device performance; Ga)(SeS)<sub>2</sub>; Two-diode model; Window layer; ZnO; Cells; Copper; Current voltage characteristics; Curve fitting; Cytology; Diodes; Gallium; Multiphoton processes; Parameter extraction; Particle swarm optimization (PSO); Semiconducting selenium compounds; Semiconducting zinc compounds; Silicon solar cells; Switching circuits; Windows; Zinc oxide; Solar cells
