Analytical Modeling and Simulation of CIGS Solar Cells

This paper deals with the development of an analytical model for simulating a polycrystalline Cu(In,Ga)Se2 (CIGS)-based thin film solar cells by a CdS(n)/CIGS(p) heterojunction structure. Consequently, a link between the characteristics of this cell and the material parameters is established. This procedure would help improving the performances of the cell. We have been investigating over this work the contribution of the space charge region in the photocurrent density which seemed to be dominant in comparison to the neutral regions. However, the increases of the buffer layer thickness only reduce the cell performances. The optimum thickness of the absorber layer was about 3 μm, a value from which the efficiency has no significant increase. The increase of the absorber bandgap reduces the optical absorption, which is reflected in the reduction of the photocurrent density. Accordingly the open circuit voltage increases as a result to the linear variation with the band gap. The compromise between these two phenomena would be a band gap of 1.55 eV which is the optimum value for obtaining a high efficiency of about 25%. All these optimization results give helpful indication for a feasible fabrication process.