Modeling Microstructure Evolution in Polycrystalline Films for Solar Cell Applications

Yunbo Wang, David R. Ely, R. Edwin García Purdue University, West Lafayette, IN, United States

Grain morphology has been long considered to be a major factor in the performance and efficiency of photovoltaic devices.  Experimental work has demonstrated the effect of average grain size and surface roughness on the control of conversion efficiency. But its statistics and kinetics are not well understood. While much theoretical progress has been made for α-Si by various effective media and Monte Carlo models, the theory of polycrystalline material growth remains primitive. In this paper, a generalized 2D model was developed to predict cell microstructure under various fabrication conditions. Growth of Cadmium Telluride was chosen due to its champion efficiency. The current model combines the numerical efficiency and elegance of the level set method to track the macroscopic interface and includes the simplicity of the phase field method to track the natural microstructure evolution for a non-conserved parameter.