Reflectance calculations of alkaline textured multicrystalline silicon: a new approach

Abstract

Alkaline texture etching is a standard procedure for manufacturing solar cells with (100) oriented single-crystalline-silicon wafers as substrates. This is performed to reduce reflectance from the wafer surface. Alkaline etching, being anisotropic in nature, results in unique texture on the surface of each crystallographic orientation of silicon. Hence, the reflectance of each grain of a multicrystalline silicon (mc-Si) substrate can be treated as a signature of its crystal orientation. This provides an opportunity to ascertain the orientation of each grain in a mc-Si wafer by the shape of the textures formed on its surface and henceforth, its corresponding reflectance. A model has been developed that can predict and create surface textures for any arbitrary crystal orientation of silicon on anisotropic alkaline etching. This model has been implemented in a computer program written in C++ to perform rigorous ray-tracing computations to calculate reflectance curves for textured silicon of any crystal orientation, wafer thickness and texture height. A database of reflectance curves for multiple crystal orientations has been built. This has led to a new and ultrafast method for grain orientation characterization using reflectance of each grain, instead of time-consuming X-ray (Laue) and Electron-backscatter diffraction measurements. The model and the algorithm used for reflectance calculations, along with some calculated results, are presented to highlight the usefulness of this procedure for application in grain orientation mapping.