Modeling and simulation of a CuGaSe/sub 2//Cu(In/sub 1-x/,Ga/sub x/)Se/sub 2/ tandem solar cell

Device modeling and simulation of a mechanically stacked CuGaSe/sub 2//Cu(In/sub 1-x/,Ga/sub x/)Se/sub 2/ (CGS/CIGS) tandem solar cell have been carried out in this study. The physical model consists of a ClGS bottom cell with a double graded band-gap profile in the space charge region (SCR) and the backside of the absorber layer and a uniform band-gap CGS top cell. By varying the absorber layer thickness of the CGS top cell, it is shown that the CGS/CIGS tandem cell could achieve an AM 1.5 G conversion efficiency of 25% with an optimized CGS and ClGS cell structure. A comparison of our simulation results with the published data for me CIGS cells shows an excellent agreement between the simulated results and the published photo-current density-voltage (J-V) and quantum efficiency (Q.E.) data for the ClGS cells.