Optimization of the CIGS based thin film solar cells: Numerical simulation and analysis

Chalcopyrite Cu(In,Ga)Se (CIGS) is a very promising material for thin film photovoltaics and offers a number of interesting advantages compared to the bulk silicon devices. CIGS absorbers today have a typical thickness of about 1–2 μm. However, on the way toward mass production, it will be necessary to reduce the thickness even further. This paper indicates a numerical study to optimization of CIGS based thin film solar cells. An optimum value of the thickness of this structure has been calculated and it is shown that by optimizing the thickness of the cell efficiency has been increases and cost of production can be reduces. Numerical optimizations have been done by adjusting parameters such as the combination of band gap and mismatch as well as the specific structure of the cell. It is shown that by optimization of the considered structure, open circuit voltage increases and an improvement of conversion efficiency has been observed in comparison to the conventional CIGS system. Capacitance–voltage characteristics and depletion region width versus applied voltage for optimized cell and typical cell has been calculated which simulation results predict that by reducing cell layers in the optimized cell structure, there is no drastically changes in depletion layer profile versus applied voltage. From the simulation results it was found that by optimization of the considered structure, optimized value of CIGS and transparent conductive oxide thickness are 0.3 μm and 20 nm and also an improvement of conversion efficiency has been observed in comparison to the conventional CIGS which cell efficiency increases from 17.65 % to 20.34%, respectively.