Fabrication of inverted pyramid structure for high-efficiency silicon solar cells using metal assisted chemical etching method with CuSO4 etchant

Inverted pyramid texture is used to improve the performance of single crystalline silicon (sc-Si) solar cell due to its excellent light-trapping properties. In this paper, inverted pyramid structures are fabricated on large area sc-Si wafers by metal assisted chemical etching method using CuSO4 instead of Cu(NO3)2. Three groups of solar cells were fabricated with textured structures prepared by CuSO4, Cu(NO3)2 and NaOH respectively. The surface microstructure, average reflectivity, surface recombination and auger recombination, internal quantum efficiency and external quantum efficiency of the sc-Si solar cells were studied in detail. The results show that CuSO4 can prepare uniform inverted pyramid structures on silicon substrate by reducing the generation of bubbles and promoting the deposition copper nano-particles on the surface of sc-Si wafer, and thus improve the properties of solar cells. More importantly, the chemical reaction mechanism for etching silicon wafer with CuSO4 and Cu(NO3)2 during the texturing process was compared and analyzed. Finally, the average efficiency of large-area sc-Si PERC solar cells fabricated by CuSO4 was 22.63%, which was 0.60% absolutely higher than that of Cu(NO3)2, and 1.56% higher than normal pyramid group.