Flat plate photovoltaics beyond silicon
Silicon solar cells account for more than 90% of the PV power installed in the world. However, their efficiency is approaching the theoretical limits and therefore further improvements will require a breakthrough in device architectures. In this context, we are investigating III-V on silicon multijunction solar cells (see Figure 1). In our approach, a GaAsP (1.7eV) top cell partners with a Si (1.1eV) bottom cell to form a dual-junction solar cell with a theoretical efficiency limit in excess of 40%. The challenges needed to engineer such a device like are manifold. To start with, there is the need to create a high quality III-V nucleation layer on silicon to serve as the template for further III-V growth. To this end, we are investigating the MOVPE growth of GaP layers on Si in a single reactor process (see figure 2). In parallel, we are also working towards defining ways to manufacture these hybrid solar cells taking the most of III-Vs and Si. Although the processing of conventional Si solar cells is a well-known technology, certain high temperature steps have been found to be incompatible with III-V semiconductors. Accordingly, we are searching for innovative low-temperature high-end processing alternatives.
Contact person: Prof. Ignacio Rey-Stolle