Improved device structures including transparent conductive oxide (TCO) and p-layers were studied for better photovoltaic performance with narrow bandgap a-Si:H solar cells prepared in p-I-n sequence on TCO-coated glass. The narrow bandgap (E-g less than or equal to 1.58 eV) a-Si:H i-layers used here were prepared by an Ar* chemical annealing technique at temperatures over 280 degreesC. Ga-doped ZnO (GZO) deposited at high substrate temperatures (250 degreesC) and microcrystalline F-layers (muc-Si:H(B)) showed improved resistance to high temperatures and Ar* bombardment-induced degradation. By employing p/i buffer layer along with these TCO and p-layers, the open-circuit voltage was increased from 0.36 to 0.56 V and the fill factor increased from 24 to 60%. In addition, enhanced red-response was observed on the narrow bandgap (E-g = 1.52 eV) a-Si:H solar cells. (C) 2001 Elsevier Science B,V. All rights reserved.