Formation of inverted pyramid-like structures on surfaces of single crystalline silicon solar cells by chemical wet etching

We present a new, simple, and cost-effective etching method for forming inverted pyramid-like structures on the surfaces of single-crystalline diamond-wire sawn silicon wafers. The method follows a three-step process for etching silicon wafers without metal-assisted chemical etching involved. We used acidic etching to produce nano-to-micro-structured caves in the first two steps followed by anisotropic etching with an alkaline solution. This paper shows that the size of the opening of the inverted pyramid could vary from several hundred nanometers to about 4 μm, depending on the etch time periods in the second and the third steps. The cell performance was, however, only evaluated here for cases of smaller sizes of inverted pyramids. That is, solar cells were manufactured following an almost commercially standard procedure by using wafers with inverted pyramids of ∼900 nm in size. The best cell with this type of structure has a conversion efficiency of 19.22%, which is higher relative to the cells with smaller inward recessed caves or upright pyramids on the surfaces.