In this work, we used the Atlas Tcad Silvaco software to investigate the effect of adding an additional BSF layer on the performance of InGap / GaAs dual junction solar cells with a hetero tunnel Al0.7Ga0.3As-In0.49Ga0.51P junction. These analyzes indicate that, the addition of a BSF layer to the bottom cell the increase in the thickness of the BSF top cell would reduce the recombination and increase the short circuit current and the efficiency. The thickness and optimal concentration of the BSF layer adds the highest cell efficiency to 56.53%. In the next step, to obtain a higher open circuit voltage, we examined the high band gap semiconductors from the шѵ group and we selected the In 0.5 (Al 0.7Ga 0.3) 0.5P semiconductor to form a hetro junction with GaAs in the bottom cell of a InGap / GaAs dual Junction solar cell. The results show photogeneration and spectral response, the InAlGap-GaAs hetero junction, transmits most of the electrons and holes produced in the top cell and low recombination in the bottom cell. For this structure, under (1sun) AM1.5, the optimal values of Voc= 2.44 V, JSC = 28.5 mA/cm2, FF =87.25 % and η= 60.89 % and finally the cell provided with other models compared.
