Investigation of Improved Performance of ZnO/CIGS-Based Solar Cells

The work presented herein shows that the performance of a CIGS-based solar cell can be improved if the toxic Cadmium Sulfide (CdS) layer is replaced with a non-toxic, environment-friendly Zinc Oxide (ZnO). The required investigation carried out in this work employs an analytical model. The model considers the load-voltage dependency of photogeneration current and surface recombination of the carriers at the emitter/absorber interface. The analytical intractability problems of the governing differential equations evolved due to these considerations. They can be resolved using the perturbation technique- a widely used method employed in the literature to resolve such issues. The developed model has been simulated in a MATLAB environment. The results obtained for CIGS solar cells with CdS and ZnO materials serving as emitters have been compared. These results demonstrate that the ZnO-based CIGS cell performs better than its CdScounterpart in Internal Quantum Efficiency (IQE) plots and current-voltage (JV) characteristics curves for a wide range of absorber width variation. The highest conversion efficiency for both these cells is observed at 1 μm, where the ZnO-based cell has a Power Conversion Efficiency (PCE) of 16.2% higher than that of the CdS-based cell (15.1%). Therefore, concerning enhanced performance and environment-friendliness, ZnO is a better option as an emitter layer of CIGS-cells than its CdS counterpart.