Influence of small size pyramid texturing on contact shading loss and performance analysis of Ag-screen printed mono crystalline silicon solar cells

摘要

Front side textured random pyramids are widely utilized in major industries for the performance enhancement of crystalline silicon (c-Si) solar cells. Random pyramids not only reduce the surface reflectance but also improve the light trapping effect. Therefore, it is necessary to understand the pyramid height affecting the cell performance, further improving cell efficiency. In this work, we present an experimental study to investigate the influence of pyramids size on the contact shading loss mechanism of silver (Ag) screen-printed p-type c-Si solar cells. Three alkaline texture solutions with sodium silicate additives were optimized to develop the small pyramid (0.5-2.0 mu m) size, middle pyramid (5.0-9.0 mu m) size and large pyramid (10-15 mu m) size on the c-Si surface, respectively. It was noticed that screen-printed finger width strongly depends on pyramid size. Even though, same mesh patterns and screen printing conditions resulted in 20 mu m widening of metal finger width on the large pyramids as compared to the small pyramids. This was attributed to the increase in the size of cell surface pyramids that not only varied the gap between the screen mesh and cell surface while screen-printing but also hindered the contraction of metal electrodes during the firing process. The c-Si solar cells with large pyramids suffered from an extra shading loss during fabrication, thus, led to the reduction of the short circuit current density (similar to 0.7 mA/cm(2)) resulting in lower efficiency (similar to 17.72%) as compared to efficiency (similar to 18.60%) of small pyramid based cells.