Analytical calculation of photocurrent density in CIGS double graded solar cell

A theoretical analysis of double-graded bandgap Cu(In,Ga)Se 2 solar cell for the simulation of the photocurrent has been developed. The photocurrent density as a function of front and back bandgaps and electron diffusion length has been calculated. Therefore, based on these concepts, optimum back bandgap is around 1.4 eV, assuming the band-gap grading in the space charge region and near the back surface region of the CIGS absorber layer with variation spatial of Ga content. The simulation results demonstrates a photocurrent approaching 35.26 mA/cm 2 .