Characterization of 2-D reflection pattern from textured front surfaces of silicon solar cells

Reflected light from textured front surfaces of a solar cell contains useful information about the surface geometry as well as the optical properties of the cell. In this study, the 2-D reflected light distributions from front surfaces of silicon cells textured in various ways are characterised by an appropriate optical setup. The results are compared to those of conventional ray tracing. For surfaces with regular inverted pyramids, we identified reflected light diffraction patterns that can be explained by the principles of geometrical optics. These reflected light patterns can be used to extract details of surface morphologies and hence be used as a tool to fine tune and monitor fabrication processes. Surfaces with random pyramids reflect light without diffraction patterns but with other distinctive features. Their reflections lie primarily in the angular range between 0º and 50º, with a maximum intensity at about 25º. The impact of the encapsulant's refractive index on the amount of total internal reflection is discussed for various types of textured surface. For both random and regularly textured surfaces, it appears possible to achieve higher total internal reflection ratio when the encapsulant's index increases from conventional 1.5 to 1.6.