TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Process: The process for producing the chalcopyrite solar cell further comprises: (f) applying the photovoltaic layer structure on chalcopyrite-basis; and (g) optionally applying an encapsulation layer (5) on the photovoltaic layer structure. In the process, after the step (d) or (e) a sodium-containing precursor layer is deposited on the polysilazane layer, preferably by vapor deposition of sodium fluoride. The chalcopyrite solar cells are manufactured on a flexible sheet-like substrate in a roll-to-roll process. Preferred Components: The solar cell is configured as a thin film solar cell and has a photovoltaic layer structure of type copper-indium-sulfide or copper-indium-gallium-selenide. The photovoltaic layer structure comprises a back contact (41) made of molybdenum, an absorber (42) of the composition of copper-indium-selenide (CuInSe2), copper-indium-sulfide (CuInS2), copper-gallium-selenide (CuGaSe2), copper-indium-gallium-selenide compounds of formula (CuIn1-xGaxSe2) or copper-indium-gallium-selenium-sulfide compounds of formula (Cu(InGa)(Se1-ySy)2), a buffer (43) made of cadmium sulfide, a window layer (44) made of zinc oxide (ZnO) or ZnO:aluminum and a front contact (45) made of aluminum or silver. The barrier layer has a thickness of 100-3000 (preferably 300-2000) nm. The barrier layer: has a specific resistance of greater than 1.109 (preferably greater than 1.1011) M Omega .cm, measured in accordance with DIN IEC 60093; and exhibits an adhesive strength of greater than 5 N, preferably greater than 10 N on the substrate, measured in accordance with a DIN-EN-ISO 2409 with an adhesive tape width of 20 mm. and The barrier layer and optionally the encapsulation layer are produced from polysilazane (I).x, y = 0-0.5.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The substrate comprises a basic material comprising metal, metal alloy, glass, ceramic or plastic. The substrate is formed as a film, preferably steel or titanium film. The barrier layer contains sodium or sodium-containing precursor layer (21).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The barrier layer comprises a hardened solution of polysilazanes and additives in a solvent, which is dibutylether. The encapsulation layer consists of a hardened solution of polysilazanes and additives in a solvent. The polysilazane solution contains at least one perhydropolysilazane. The polysilazane solution contains a catalyst, and optionally further additives. The polysilazane solution contains sodium, preferably in the form of sodium acetate or sodium tetraborate.