We have employed a one-step (direct etching) metal-assisted chemical etching (MACE) technique to grow large-area Si nanostructures with smoother surface morphology and much less porous Si (PS) defects than those under the two-step (depositing and etching) MACE. A 17.63%-efficiency of the nano/microstructures (N/M-Strus) based multicrystalline Si (mc-Si) solar cells has firstly surpassed that (17.45%) of traditional-micro-textured one with a standard solar wafer size of 156 x 156 mm(2). The key to success lies in the reduction of electrical loss by removing PS defects and employing shorter one-step-MACE-smoothened N/M-Strus, together with the optical gain from the combined antireflection of mc-Si N/M-Strus and SiNx:H thin films. The present work opens a way to the mass production of high efficient Si nanostructures based solar cells with a less-process-step and lower-cost approach. (c) 2015 Elsevier B.V. All rights reserved.