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.