A photovoltaic cell is proposed. The photovoltaic cell includes a substrate of semiconductor material, and a plurality of contact terminals each one arranged on a corresponding contact area of the substrate for collecting electric charges being generated in the substrate by the light. For at least one of the contact areas, the substrate includes at least one porous semiconductor region extending from the contact area into the substrate for anchoring the whole corresponding contact terminal on the substrate. In the solution according to an embodiment of the invention, each porous semiconductor region has a porosity decreasing moving away from the contact area inwards the substrate. An etching module and an electrolytic module for processing photovoltaic cells, a production line for producing photovoltaic cells, and a process for producing photovoltaic cells are also proposed.