In this work we present the results we obtained by processing 1 Ωcm p and n‐type, multi‐crystalline silicon wafers when a double hydrogenated amorphous/crystalline silicon heterojunction is applied to sandwich the substrate, at the sunward surface to form the emitter and at the rear side to act as back surface field. We have investigated the role of the multi‐crystalline silicon surface conditioning, on the base of illuminated and dark current‐voltage characteristic, quantum efficiency measurements, and overall photovoltaic solar cell performance. In particular, a comparison between an acidic isotexturing and a chemical polishing treatment is presented and discussed in detail. We have found that the morphology of the multi‐crystalline silicon surface plays a tough role in the a‐Si:H properties when used as surface passivating layer. The commercial acidic surface treatment, commonly used in diffused junction mc‐Si …