Projected Efficiency of Polarization-Matched p-In $_{\bm x}$ Ga $_{\bm {1-x}}$ N/i-In $_{\bm y}$ Ga $_{\bm{1-y}}$ N/n-GaN Double Heterojunction Solar Cells

Traditional p-GaN/i-InGaN/n-GaN double heterojunction solar cells have limited power conversion efficiency due to large polarization charges that accumulate at the heterojunction interfaces, leading to severe band bending that, in turn, hinders the carrier transport. In this study, we proposed the use of a p-type InGaN layer to reduce the polarization field and projected the power conversion efficiencies of p-In xGa1-xN/i-In yGa1-y N/n-GaN double heterojunction solar cells that are grown on a c-facet sapphire substrate with various indium components. Numerical simulations predict that a maximal power conversion efficiency that is close to 7% with a short-circuit current density of 4.05 mA/cm2 and an open-circuit voltage of 1.94 V can be achieved with a p-In0.2 Ga0.8N/i-In0.2Ga0.8N/n-GaN structure due to a polarization-matched p-i interface. Further efficiency enhancement with a higher indium composition over 20% is also possible via the redistribution of the built-in potential with n-GaN doping.