Establishing Baseline Models for High Efficiency CIGS Photovoltaic Devices

Solar cells based on the compound Copper Indium Gallium Diselenide, Cu(In_xGa_1-x)Se₂, (or CIGS) are commercially important.  As a quaternary compound, the electronic properties of CIGS can be controlled by varying the composition.  Our work involves numerical analysis to establish four CIGS baseline device models for comparison to published data.  These models include mid-gap defect concentration and band gap profiles that are Ga dependent.  The models also consider the effects of metastable/multivalent defects.  Numerical calculations of current-voltage (JV), quantum efficiency (QE), and capacitance-voltage (CV) were carried out using one dimensional simulation program SCAPS-1D. The results are compared to published data for a reference cell and calculations for similar models.  Simulated efficiencies reached 20.1% -20.8% depending on the model. In subsequent work, the baseline models will be used to test various hypotheses regarding the electronic structure of the CIGS/buffer interface region.