Design optimization of single-layer antireflective coating for GaAs_1-xP_x/Si Tandem Cells with x=0, 0.17, 0.29, and 0.37

Single-layer antireflective coating (SLARC) materials and design for GaAs_1-xP_x/Si tandem cells were analyzed by TCAD simulation. We have shown that optimum SLARC thickness is a function of bandgap, thickness, and material quality of top GaAs1-x subcell. Cells are analyzed for P fractions x =0,0.17, 0.29, and 0.37, and ARC materials: Si₃N₄, SiO₂, ITO, HfO₂, and Al ₂O₃. Optimum ARC thickness ranges from 65-75 nm for Si₃N₄ and ITO to ∼100-110 nm for SiO₂. Optimum ARC thickness increases with increasing GaAs 1-x\bf P x absorber layer thickness and with decreasing P fraction x. Simulations show that optimum GaAs1-x Px absorber layer thickness is not a strong function of ARC material, but it increases from 250 nm for x =0 to ∼1 μm for x ={\bf 0.29 and 0.37. For all P fractions, Si₃N₄, HfO₂, and Al₂O₃ performed almost equally, while SiO₂ and ITO resulted in ∼1% and ∼2% lower efficiency, respectively. Optimum SLARC thickness increases as the material quality of the top cell increases. The effect of ARC material decreases with decreasing GaAs1-x}}Pbm x}material quality. The maximum efficiencies are achieved for cells with ∼1-μm GaAs_0.71P_0.29 absorber (τ = 10 ns): ∼26.57% for 75-nm Si₃N₄ SLARC and 27.62% for 75-nm SiO₂/60-nm Si₃N4 double-layer ARC.