The effect of front pyramid heights on the efficiency of homogeneously textured inline-diffused screen-printed monocrystalline silicon wafer solar cells

Abstract

The majority of industrial monocrystalline silicon (c-Si) wafer solar cells are alkaline textured (at least the illuminated surface) to reduce reflection and increase absorption of incident light. Therefore, understanding the influence of front pyramid heights on the solar cell parameters is essential for further improving cell efficiency. In this work we report the impact of pyramid height on the performance of inline-diffused c-Si solar cells. Three alkaline texture processes with potassium silicate additives are optimised to result in homogeneous coverage of pyramids. By modifying the process, surface textures with small (∼5 μm maximum), medium (∼6 μm maximum) and large (∼8 μm maximum) pyramid heights are formed. The impact of pyramid size on cell parameters is experimentally studied using industrial-grade 156-mm pseudo-square p-type Czochralski wafers. It is found that within the pyramid size range studied here, there is no significant variation in effective minority carrier lifetime, reflectance, open-circuit voltage or short-circuit current. However, fill factor and hence efficiency is significantly impacted by pyramid size. While cells in all three groups demonstrate high fill factor (>79%), it is shown that an average fill factor gain of up to 1% absolute can be achieved by using the best-suited texture process.