Significant advances have been made in the recent years to improve the efficiency of single- and multi-junction solar cells incorporating nanocrystalline silicon (nc-Si:H). The improvements have resulted from the development of high quality intrinsic material, novel doped layers, superior back reflector and appropriate device design. Stable active-area efficiency of 13.6% for small-area cells and aperture-area efficiency of 11.85% for large-area devices have been achieved. In this paper, we discuss the key activities that led to these high efficiencies with emphasis on substrate-type solar cells. Manufacturing issues and future research directions to improve efficiency further are also discussed, (C) 2013 Elsevier B.V. All rights reserved.