We investigate the improvement of p-i-n type thin-film silicon (Si) solar cells by employing a hydrogenated n-type amorphous Si (n-a-Si:H)-based bilayer. The initial conversion efficiency (eta) of a-Si:H single-junction solar cells is improved from 9.2 to 10.0%. The developed n-a-Si:H-based bilayer is also suitable for a-Si:H/hydgrogenated microcrystalline Si (mu c-Si:H) double-junction solar cells, and thus initial eta is improved from 10.4 to 10.8%. With a further optimization, initial eta of 11.3% and stabilized eta of 10.1% are achieved. Since the n-a-Si:H-based bilayer is easily formed using a conventional process, it can be a promising option for cost-effective mass production of large-area thin-film Si solar modules. (C) 2013 Elsevier B.V. All rights reserved.