Thin Black Silicon Solar Cells

Abstract

Solar power is an already well-established renewable energy type, which is used in many places globally. Commercial solar cells are typically made of silicon, due to the amount of knowledge concerning silicon semiconductor technology. Even though scientific research has come up with many possible solutions for increased efficiency of solar cells, they are in general very complicated to fabricate, and as a consequence more expensive than conventional cells, rendering it impossible for such a solar cell to be competitive on the solar cell marked. One way of making a competitive cell could be by material savings, and thereby being able to offer the same efficiency and power, for a lower price. Today for solar cells, the largest expense in fabricating the cells is the silicon cost. This will for a 200 μm cell correspond to about 81 % of the total cost. Our idea is to save material and cost of the solar cell by making the solar cells thinner, which will lead to less pollution due to the optimized use of silicon. By implementing the surface structuring known as black silicon for minimizing reflection, we at the same time expect to have a higher efficiency than conventional solar cells. Conventional solar cells have a surface structure defined by a KOH etch, which etches as deep as 30-40μm. With the RIE black silicon etch we will at most etch 1 μm away, resulting in a significant material saving. In the end, we expect to only use ¼ of the silicon used in conventional cells.