A perspective of GaAs//Si tandem photovoltaic cell: Architecture, fabrication, and performance

Tandem solar cells utilize multiple semiconductor layers with complementary bandgaps to capture a broader solar spectrum, overcoming the efficiency limits of single-junction cells. The article reviews the architecture, fabrication, and performance of GaAs//Si tandem solar cells, emphasizing material developments, optical coupling, and electrical connections in tandem configurations. The fabrication section elaborates on active layer deposition, doping techniques, and interconnecting layers. Deposition techniques like chemical vapor deposition and molecular beam epitaxy are preferred for GaAs deposition to reduce the lattice mismatch between GaAs and Si. Zn and Si are the cost-effective doping elements for GaAs by metalorganic chemical vapor deposition and ion implantation. AlGaP, InGaP, and ZnO are the typical window layers, acting as front passivation for the GaAs top cell. The graded composition of III-V compounds acts as the buffer layer to connect the GaAs top cell to the Si bottom cell in two terminal monolithic configurations.