Pre-texturing multi-crystalline silicon wafer via a two-step alkali etching method to achieve efficient nanostructured solar cells

•As-cut mc-Si wafer can be isotropically etched by a two-step alkali-etch process.•Flat wafer surface benefits homogenous nanostructure and cell's performance.•Mean efficiency of N-DRE Bmc-Si cells reach 18.63%, 0.6% higher than normal ones.•Isc and Voc voltage were improved simultaneously in N-DRE Bmc-Si solar cells.•High Voc of N-DRE Bmc-Si solar cells is contributed to small dark current I0.

Alkali solutions are not suitable for texturing multi-crystalline silicon (mc-Si) wafer due to the anisotropic etching. In this study, a two-step alkali-etch process is developed to form a flat surface on the wafer, which can be quickly and nearly isotropically etched by immersion in a sodium hydroxide solution, followed by a sodium hydroxide-sodium hypochlorite solution. The etching process leads to the formation of homogenous nanostructure, thereby improving the cell's repeatability and performance by simultaneously increasing its short-circuit current and open-circuit voltage.