In-situ determination of the effective absorbance of thin μc-Si:H layers growing on rough ZnO:Al Matthias Meier, Karsten Bittkau, Ulrich W. Paetzold, Jürgen Hüpkes, Stefan Muthmann, Ralf Schmitz, Andreas Mück and Aad Gordijn EPJ Photovolt., 4 (2013) 40602 Published online: 02 October 2013 DOI: 10.1051/epjpv/2013025