High efficiency of two solar cells CIGS/CIS stacked mechanically

In our work, we have simulated and optimized solar cells based on the mechanically stacked system using the Analysis of Microelectronic and Photonic Structures (AMPS-1D) simulator in respect to overall performance. The structures of solar cells are based on the top cell Copper- Indium- Gallium- diselenide, CuIn 1-x Ga x Se 2 , referred to as CIGS, and the bottom cell Copper- Indium- Gallium, CIS. We have simulated each cell individually and extrapolated their optimal parameters (thickness, concentration of absorber). In the case of tandem, we calculated the efficiency of each cell optimized by separation of the solar spectrum in bands where the cell is sensible for the absorption. The current-matching limitation imposed by series connection reduces efficiency relative to independently-connected cells.