Effect of surface cleaning on pyramid size of randomly textured mono crystalline silicon and the impact on solar cell efficiency

In this paper we report on the use of cleaning chemistry, SunSource™68 developed by Air Product Chemicals, Inc., (APCI) to control random texturing time and pyramid size on mono-crystalline silicon wafers. This chemistry is applied immediately after saw damage removal, which removes residues and acts as a catalyst to initiate texturing very rapidly. Due to rapid nucleation, the amount of IPA needed in the solution is very small and our texturing time is cut down by half. Thus the amount of silicon removed as a result of texturing is ~45% less than the standard texturing without the clean and this increases the texturing bath life. We have applied this cleaning chemistry before texturing and compared with the standard texturing process. The use of the cleaning solution has produced uniform pyramids across a wafer and from wafer to wafer, irrespective of wafer vendor. We found, repeatedly and reproducibly, ~0.5% efficiency improvement with the cells made in conjunction with the cleaning chemistry. This improvement resulted from a combination of lower weighted reflectance and narrow gridlines resulting from uniform and small pyramids associated with the cells using cleaning chemistry. We have demonstrated an 18.3% average efficiency large area (239 cm²) cells on 2.6 Ω-cm CZ Si compared to 17.8% for the standard textured cells.