The most efficient technology for generation of electricity from solar irradiation is multijunction solar cell in tandem structure. The materials used in these structures are a prime factor, controlling device efficiency. The III-V compound semiconductor optoelectronic alloys are quite promising, due to their direct bandgap feature and superior performance, compared to any other existing solar cell technologies. This has led to a widespread use of these alloys in solar panels installed in satellites. In spite of superior performance of III-V alloy cells, Si cells have dominated the terrestrial market due to their lower cost. To introduce cost effectiveness in tandem cells Al is alloyed with GaInP and GaAs, in the proposed structures, which bring down the cost of these priceless alloys. Moreover, a comparative analysis is done among double and triple junction cells. The aim of this work is to investigate and correlate their performance in terms of efficiency, fill factor, and other electrical parameters, in double junction and triple junction solar cell on Germanium (Ge) substrate. Dark current of these two cells are also calculated for analyzing their performance.