Simulation study for the current matching optimization in In0.48Ga0.52N/In0.74 Ga0.26N dual junction solar cells

In this paper indium gallium nitride (InGaN) is used to design and optimize a dual junction (DJ) solar cell, which is series-connected via a tunnel diode, with a careful analysis of the current matching between the top and the bottom sub-cells. In particular, a bandgap combination of 1.76eV/1.13eV for an In0.48Ga0.52N/In0.74Ga0.26N structure is adopted and several numerical simulation results are presented. The doping concentration and the base thickness of each sub-cell are considered as fitting parameters in order to determine an accurate current matching condition. The In0.48Ga0.52N-based n++/p++ tunnel junction behavior is also taken into account. A maximum short circuit current density of 19.543 mA/cm2 is obtained for a 1µm-thick base in both the sub-cells, and a p/n doping ratio of 5×1018 cm 3/5×1015 cm-3 and 1.9×1019 cm 3/1.9×1016 cm 3 for the top and the bottom cell, respectively. The optimized DJ solar cell exhibits an open circuit voltage of 1.713 V, a fill factor of 82.49%, and a conversion efficiency of 28.78%. The external quantum efficiency and the current (power) density-voltage characteristics of different devices are investigated in detail.