Photovoltaic (PV) power generation is becoming widespread as a clean and gentle energy source for the earth. The main drawback of currently used photovoltaic cell is its low conversion efficiency and materials with the appropriate band gaps that can perfectly match the broad range of solar radiation. Recently it has been shown that the energy gap of InxGa1-xN alloys potentially can be continuously varied from 0.7 to 3.4 eV, providing a perfect matching to the full-solar-spectrum. Therefore, InxGa1-xN becomes a promising material for very high efficiency multijunction solar cell. Any desired value of bandgap can be obtained from this material choosing the appropriate composition. In this work, InxGa1-xN-based multijunction solar cells have been designed theoretically for high efficiency and the performance of the designed solar cells are evaluated with various parameters.