In this work, we focus on ZnO:B layers as an alternative TCO for application on a-Si:H/c-Si heterojunction solar cells. First, the optimization of the material has been done in terms of optical and electrical properties. We have also studied the behaviour of ZnO:B against ageing. Finally, complete heterojunction solar cells have been fabricated with different back-side TCO configurations to understand the ageing mechanisms and to deeply study the influence of degradation on the solar cells parameters. Stable efficiencies up to 16.6% on polished n-type c-Si were obtained on 25 cm(2) heterojunction solar cells fabricated at low temperatures. (C) 2010 Elsevier B.V. All rights reserved.