Chemical Texturization Processes for Non-conventional Silicon Substrates for Silicon Heterojunction Solar Cell Applications

The present work addresses the exhaustive study of the surfaces of multicrystalline silicon wafers after being subjected to a texturization process for silicon heterojunction solar cell applications. The investigations described include the effect that the time of isotropic etching based on combinations of hydrofluoric and nitric acids has on the reflectance, the morphology of the surfaces and the surface recombination through the evolution of the implicit open-circuit voltage. The influence of previous treatments and the elimination of porous silicon or silicon oxide formed on wafer surfaces as a consequence of these texturization processes are also addressed. Textured multicrystalline silicon wafer surfaces with a good uniformity and low weighted hemispherical reflectances (23–24%) have been achieved with short etching times. These texturization processes have also been tested on upgraded metallurgical silicon wafers, resulting in weighted hemispherical reflectance values around 23%, but at the cost of the appearance of important surface defects.