At the cell’s level the efficiency must be increased as much as possible. There are many different technology developments that lead to cell’s conversion efficiency improvement. Additionally, the cost of cell manufacture must be reduced, both through material usage reduction (design changes, increase of concentration factors, etc.) and improvements to the production process.
The multi-junction III-V cells that are going to be used, have been realised with structures in which several semiconductor junctions (at least 3 junctions) are built up in successive layers, each of which, being sensitive to a certain portion of the solar spectrum, can separately convert the corresponding energetic component. The 3 junctions are made of materials that can be grown epitaxially ‘lattice matched’ and without generating crystal defects at the interfaces between the different layers, which act to reduce the voltage and efficiency of the resulting solar cells.
Ecosole has studied, in collaboration with the main cells manufacturers, the optimization of the multi-junction cell’s performance. Standard manufacturing grade cells with conversion efficiency beyond 42% have already been tested and are being further optimized.
