Hybrid Dual Junction Silicon Based Solar Cell

A III-V solar cell has been made on top of a Silicon substrate. The main focus of the project has been to reduce the number of defects that originates from the interface between the Silicon and the III-V material. This has been done by combining substrate, its preparation and special growth parameters for the III-V material. Simulations on a dual-juction solar cell structure with a Silicon solar cell at the bottom and a III-V solar cell at the top, has been done. The simulations show that we can increase the efficiency of the Silicon solar cell by adding a III-V solar cell on top and include optical elements. The next step of the project is to show both solar cells in a double-junction structure and determine the total conversion efficiency of the double solar cell.

The underlying idea of the project is to build dual junction tandem solar cells by deposition of III-V structures on monocrystalline Si substrates. With conventional approaches for III-V film deposition, the defect density of the overlayer would be too hi gh to allow for practical solar cell operation. These defects are naturally formed in crystalline interfaces where the two crystals have a large mismatch in lattice parameters. Integrated Solar has, however, developed a patented deposition procedure that ensures that the defect density of the resulting epitaxial III-V film remains low. The prospect for solar cell devices with efficiencies at 30% without solar concentration, justifies the additional costs related to the introduction of III-V growth process es in an otherwise standard Si wafer solar cell production line.