Investigation of the electronic properties of the recombination heterointerface in CGS/CIGS monolithic tandem solar cell

We have investigated, by means of numerical simulation, the possible nature of the recombination heterointerface in the monolithic CGS (top)/CIGS (bottom) tandem solar cell. The results show that current transport by tunnelling might be of less importance. On the other hand, a good recombination junction can be achieved by a formation of a semi–metal at the back contact. It is proposed that a thin interlayer of MoSe2, which is of semi–metallic nature, is introduced at the CGS back contact in order to have a good ohmic contact between the two cells in the tandem. Numerical simulation of the tandem structure reveals that there exists an optimal thickness of the top absorber. The most probable limitations of the efficiency of this tandem structure are a low open circuit voltage and a low fill factor.