The purpose of this paper is to show an innovative and complete fabrication sequence of thin film photovoltaic modules based on hydrogenated amorphous silicon on non transparent substrates (high roughness low carbon steel). This fabrication sequence is oriented to monolithically interconnected modules with two main challenges (i) the development of surface treatment technology (low cost intermediate inorganic coatings based on sol-gel technology) for the deposition of thin film solar cells on non transparent substrates and (ii) the use of novel laser scribing methods in substrate configuration. After the research carried out in this work, we demonstrate that (i) surface treatment technology has been successfully developed proving its good behavior in 1 cm(2) steel solar cells achieving efficiencies close to 7%, and (ii) laser scribing method has also been succeeded achieving efficiencies higher than 3% in 64 cm(2) modules. Electrical losses due to these processes have been evaluated. It is important to point out that, although silicon based technology has been used, these advances are not directly related to any specific thin film solar technology, being suitable for CIGS and CdTe solar cells. (C) 2015 Elsevier Ltd. All rights reserved.