An improved optical simulation method for crystalline silicon solar cells

The combination of light reflectance, light trapping and absorption plays an important role in the conversion efficiency of solar cells. An accurate modeling of these parameters is paramount for optimizing solar cells through simulation. In the past, optical simulations have suffered from lack of accuracy. In particular, quality of texturization, non-specular reflection on the back surface and free carrier absorption (FCA) has been difficult to simulate. An improved optical simulation method is introduced in this paper. Based on the image of the textured front surface, obtained from scanning electron microscope (SEM), a three-dimensional model is automatically generated for Sentaurus TCAD simulator. The roughness of the rear side of the cell creates non-specular reflection of infra-red light, which is simulated by combining a three-dimensional pyramid structure and Phong's model. Free carrier absorption is introduced after measurement of the doping profiles. A good fit between measured and simulated reflectivity data over a wide range of wavelengths is demonstrated, resulting in a reliable optical generation profile for the subsequent semiconductor device simulation.