In this model we investigate theoretically the characteristics of multi junction InxGa1-xN series-connected solar cells under air mass 1.5 global irradiance spectrum using Matlab program. The doping levels of p-type and n-type were 5x10^18 cm^-3 and 1x10&18 cm^-3 respectively. The efficiency is found to be varied from 18.01% for single junction to 42.55% for five junctions. The enhancement in Voc was observed from the lower values of total thickness.
