Appearance of rift structures created by acidic texturization and their impact on solar cell efficiency

For effectively textured silicon surfaces for solar cell applications two sometimes contradicting preconditions have to be met. On the one hand a roughening of the surface which reduces the amount of incident light reflected on the surface and leads to higher short circuit currents and on the other hand a minimization of the total surface area which results in higher open circuit voltages. Acidic texturing of multi-crystalline silicon (mc-Si) wafers often leads to rough surfaces with strong etch attacks (rift structures) especially at crystal defects. However, in this work we come to the conclusion that, besides the rift structures slightly increase surface area and might also decrease parallel resistance, they do not have a significant influence on solar cell efficiency as well as on open circuit voltage, short circuit current and fill factor. Moreover, the rift structures are an indicator for material quality. Furthermore, in this work is has been found that for these acidic created textures surface roughness correlates with weighted reflection and hence only one of these parameters has to be measured.