TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The electrode layers and photovoltaic-active layer are encapsulated in a suitable encapsulant, where the back-plane comprises the film. The film is an opaque or white film, where the film is present outermost in the multi-layer assembly.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The hydrolysis stabilizer is present at 0.1-2 wt.%, relative to the total weight of the layer. The hydrolysis stabilizers in the polyester film consists essentially of at least one glycidyl ester of a branched monocarboxylic acid. The branched monocarboxylic acid: has 5-15C; is saturated; and/or is a synthetic material. The hydrolysis stabilizer is manufactured by the reaction of epichlorohydrin with the branched monocarboxylic acid. The hydrolysis stabilizer is substituted acetic acid oxiranylmethyl ester compounds of formula (I). The polyester film further comprises: an organic UV-absorber, preferably benzophenones, benzotriazoles, benzoxazinones or triazines; and an anti-oxidant. The UV-absorber is present at 0.1-10 wt.% relative to the total weight of the layer.R1, R2 = alkyl, preferably CH3; andR3 = H or alkyl (preferably alkyl).Provided that: the total number of C in R1-R3 is 3-48, preferably 3-13; and when R1 is CH3, and R2 and R3 are alkyl, the total number of C in R2 and R3 is 7.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The intrinsic viscosity of the polyester in the polyester film is at least 0.65, preferably at least 0.8. The polyester of the polyester film exhibits an endothermic high temperature peak at a temperature of (A) degrees C and an endothermic low temperature peak at a temperature of (B1) degrees C, where the both peaks are measured by differential scanning calorimetry, and the difference of (A) and (B1) (i.e. (A)-(B1)) is 15-50 degrees C. The polyester film exhibits an elongation to break, measured according to ASTM D882, of at least 10% after at least 56 hours, preferably at least 84 hours when aged at 121 degrees C and 1.2 bar pressure. The polyester film is white. The polyester film has an additional polymeric layer disposed on a first surface of it, where the additional polymeric layer is a polyester layer optionally comprising at least one additives comprising hydrolysis stabilizer(s), UV-absorber(s), anti-oxidant(s) or particulate inorganic filler(s), and preferably the second layer exhibits a haze of not greater than 50%. Preferred Process: The process further comprises manufacturing the hydrolysis stabilizer by the reaction of epichlorohydrin with the branched monocarboxylic acid. The hydrolysis stabilizer is reacted with the polyester by injecting the additive into the molten polymer prior to: the polymer being cast into a film; or extruding the layer. EXAMPLE - A masterbatch was prepared as hydrolysis stabilizer onto polyethylene terephthalate (PET) chip containing barium sulfate (18 wt.% based on the weight of the polyester). The mixture was then heated, extruded and repelletized. The concentration of hydrolysis stabilizer in the masterbatch was 5.8 wt.% relative to the total weight of the composition. The masterbatch was then added to PET chip in the hopper of a twin-screw extruder (with vacuum to remove moisture) at pre-determined dilutions to provide the final film with hydrolysis stabilizer. The mixture was melt extruded at 285 degrees C, cast onto a cooled rotating drum and stretched in the direction of extrusion to approximately 2.9 times its original dimensions at 86 degrees C. The cooled stretched film was then passed into a stenter oven at 110 degrees C, where the film was dried and stretched in the sideways direction to approximately 3.4 times its original dimensions. The biaxially stretched film was heat-set at either 220 degrees C or 235 degrees C to give the white film with a final thickness of 50 mu m.