Investigation of improved PV parameters through AMPS-1D in micromorph tandem solar cells with a microcrystalline tunnel recombination junction

The quest of higher conversion efficiencies of solar cells has led to the improvement of material properties and the design of new structures for a better use of the solar spectrum. One of the most promising thin-film silicon solar cell concepts is "Micromorph" tandem solar cells consisting of a microcrystalline silicon bottom subcell and an amorphous silicon top subcell. In this paper, a micromorph tandem solar cell (alpha-Si:H/mu cSi:H) with an intermediate microcrystalline tunnel recombination junction (TRJ) has been designed and analyzed by simulations using AMPS-1D (Analysis of Microelectronic and Photonic Structures) device simulator. A higher efficiency for the micromorph tandem has been achieved by optimizing each subcell and the TRJ. The open-circuit voltage V-OC is improved and it is nearly the sum of the V(OC)s of the two corresponding subcells. However, the fill factor FF and short-circuit current J(SC) are lower in comparison to the single amorphous solar cells. The spectral response behavior of the micromorph tandem has shown better utilization of solar spectrum.