Simulation study of an optimized current matching for In0.39Ga0.61N/In0.57Ga0.43N/In0.74Ga0.26N triple-junction solar cells

This paper deals with the design and optimization of a triple-junction (TJ) solar cell using indium gallium nitride (InGaN) material. Two tunnel diodes are used to ensure connection between the different subcells. A comprehensive study is performed by means of 2D numerical simulations to locate the best bandgap combination that leads to an optimized current matching. During the simulations, the doping concentration and the base thickness are considered as fitting parameters for the top and the middle subcells. The In0.39Ga0.61N/In0.57Ga0.43N/In0.74Ga0.26N bandgap combination is supposed to be 2.02 eV/1.52 eV/1.13 eV. A high short-circuit current density (13.313 mA/cm2) is achieved by assuming a base thickness of 1 µm for each subcell and a p/n doping ratio of 5 × 1018 cm−3/5 × 1015 cm−3 in the top cell, 1.5 × 1019 cm−3/1.5 × 1016 cm−3 in the middle cell, and 7.5 × 1018 cm−3/7.5 × 1015 cm−3 in the bottom cell. The optimized structure has an improved open-circuit voltage (2.877 V), fill factor (83%), and conversion efficiency (33.11%).