TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - 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 encapsulation layer has a thickness of 100-3000 (preferably 300-2000) nm. A barrier layer (2) on the basis of polysilazane is disposed between the substrate and the photovoltaic layer structure. The solar cell has an average relative reflectivity of less than 97%, preferably less than 95%, for light in the wavelength range from 300-900 nm before application of the encapsulation layer. The solar cell has an average relative reflectivity of more than 120%, preferably more than 200% for light in the wavelength of 1100-1500 nm before the application of the encapsulation layer. The solar cell has an efficiency of greater than 70%, preferably greater than 80%, based on the output value, in an accelerated aging test according to DIN EN 61646 after 800 hours. The chalcopyrite solar cells are manufactured on a flexible sheet-like substrate in a roll-to-roll process. The encapsulation layer and optionally the barrier layer consists of cured solution of polysilazane and additives in a solvent, which is dibutyl ether. The substrate consists of an electrically conductive material, and that consists of one or more of the layers from which the photovoltaic layer structure (4) which have been deposited galvanically.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 polysilazane solution contains at least one perhydropolysilazane. The polysilazane solution contains a catalyst, and optionally further additives.