A Simulation Tool for Ion Transport in Thin Film Semiconductors*

Cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) are the key materials used in the fabrication of thin-film photovoltaic devices. Migration of ions plays a significant role in the performance and degradation of such devices and is a topic of continuing research. This work focuses on diffusive transport in crystalline and polycrystalline solids with special attention to grain boundaries.   The role of ion migration such as copper and phosphorous in CdTe and sodium in CIGS is reviewed using a general numerical simulation tool in this work. COMSOL Multiphysics® software is used to perform calculations using the finite element method. The output of this numerical modeling is validated against literature data.  In addition, results of an empirical analysis will be presented for the case of sodium diffusion in polycrystalline CIGS.  The extension of this work could be to enhance the capabilities of a device simulator by incorporating such ion transport mechanisms.