Optimization of InGaN-based solar cells by numerical simulation: Enhanced efficiency and performance analysis

The development of efficient solar cells is limited by the inability of the materials to absorb light from the entire solar spectrum. InGaN solar cells have become promising, due to the broad bandgap coverage of the solar spectrum from 0.7 eV to 3.42 eV. The performance of InGaN devices is simulated using SCAPS-1D software. The impacts of layer thickness and defect density on the performance of p-n and p-p-n junction InGaN solar cells were investigated, including holistic optimization of power conversion efficiency and quantum efficiency. A notable observation was the improvement in conversion efficiency with rising indium content, peaking at 23.8 % for In0.6Ga0.4N. For p-p-n junction cells, a thicker p-layer plus an additional thin top p-layer with a larger bandgap proved advantageous. The n-layer defect density in p-n junction cells showed minimal effects on open-circuit voltage and fill factor but reduced short-circuit current and efficiency as it increased. Conversely, the p-layer defect density influenced performance only at high densities beyond 1016 cm−3, while for p-p-n junctions, the top p-layer's defect density had minimal impact. The optimized designs for both p-n and p-p-n junction cells, incorporating graded bandgaps, achieved optimal conversion efficiencies of 33.89 % and 34.07 %, respectively. The p-p-n design showed an enlarged high-efficiency area for suitable indium concentrations, offering broader indium concentration tuning possibilities and better lattice constant tuning. Quantum efficiency evaluations show the differences of defect densities and thicknesses across specific wavelength intervals, reaffirming the potential for strategic cell design choices.