Design of anti-reflection coating for surface textured interdigitated back contact silicon hetero-junction solar cell

Abstract

An all low temperature (<;300°C) processed stack structure consisting of amorphous silicon (a-Si), silicon nitride (a-SiNx) and silicon carbide (a-SiC) has been proposed for antireflection (AR) and surface passivation for interdigitated back contact (IBC) silicon hetero-junction solar cell. To reduce surface reflection and enhance photo current collection, the AR coating stack needs to be carefully designed accounting for the surface texture. In this work, the surface texturization of crystalline silicon (c-Si) using tetramethyl ammonium hydroxide (TMAH) solution was investigated. The most effective textured surface in terms of weighted reflectance was selected for AR coating. A 2-dimensional analytical modeling of the random pyramid-like surface textured morphology was based on scanning electron microscopic (SEM) images and verified by fitting bare textured Si reflection spectra with experiments. A ray tracing procedure was then used to optimize thicknesses and deposition recipes for the individual layers in AR stack. Two optimized stack structures with a 5nm thick a-Si layer were obtained, both yielding a maximum photo current of 40 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for IBC solar cell, while ensuring satisfactory surface passivation quality. The photo current losses of optimized AR stacks were also discussed.