TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The polymer (I) possesses an amount of unstable end-groups of -COF type of less than 0.1 mmol/kg; 17 to 23 wt.% of recurring units derived from MVE. The polymer (I) possesses a melting point (Tm2) from 215 to 230 degrees C, measured according to ASTM D 3418; a melt flow index (300 degrees C/5 kg) of from 5 to 30 (preferably 10 to 20) g/10 minutes using ASTM 1238-01. The back layer comprises a fluoropolymer compatible with polymer (I). Preferred Method: The process involves (i) providing a bidimensional photovoltaic element having a surface (S1); (ii) providing a sheet comprising polymer (F) having a surface (S'), and a back layer having a surface (S''), surfaces (S') and (S'') which is suitable to extend beyond perimeter of surface (S1); (iii) assembling the sheet with the photovoltaic element and a back layer so that the light receiving surface of the photovoltaic element is entirely covered by the sheet and the back surface of the photovoltaic element is entirely covered by the back layer, and that the sheet and the back layer are in intimate contact all around the periphery of the surface (S1) of the photovoltaic element, so as to provide an assembly; (iv) submitting the assembly to a thermal treatment at 230 degrees C. The thermal treatment (iv) is followed by a controlled cooling step (v) where the assembly, after being heated at a first temperature T1, is cooled: from T1 to a second temperature T2 equal to T1-100 degrees C with a cooling rate of less than 30 degrees C/minute, preferably of less than 15 degrees C/minute from T2 to room temperature with a cooling rate of less than 15 degrees C, preferably of less than 10 degrees C/minute. The process involves (i) providing a bidimensional photovoltaic element; (ii) heating the photovoltaic element to at least 230 degrees C; (iii) spraying the heated surfaces of the photovoltaic element with a composition comprising () so as to homogeneously coat the photovoltaic element.