Lattice mismatched five-junction solar cell and preparation method thereof

The invention discloses a lattice mismatched five-junction solar cell and a preparation method thereof; a GaInP nucleating layer, a GaInAs buffer layer, an AlGaInAs DBR reflecting layer, an AlGaInAs lattice gradient buffer layer, a first GaInAs sub-cell, a second GaInAs sub-cell, a first GaInP sub-cell, a second GaInP sub-cell and a GaInAs cap layer are sequence formed on a Ge substrate; the GaInPnucleating layer, the GaInAs buffer layer and the AlGaInAs DBR reflecting layer are in lattice matching with the Ge substrate; the epitaxial layers of the first GaInAs sub-cell, the second GaInAs sub-cell, the first GaInP sub-cell and the second GaInP sub-cell are in lattice mismatch with the Ge substrate, and lattice matching is kept between the epitaxial layers. According to the solar cell andthe method, the sub-cell carrier collection efficiency and a cell filling factor can be effectively improved, so that the photoelectric conversion efficiency of the five-junction solar cell is improved; compared with most five-junction cells, the structure does not need to grow a GaInNAs epitaxial layer with high quality and harsh growth conditions, and the product development difficulty and the large-scale growth cost are greatly reduced.