TECHNOLOGY FOCUS - POLYMERS - The surface protection sheet is made of glass, fluorinated resin, or cyclic polyolefin, polycarbonate, poly(meth)acrylate, polyamide or polyester resin. The polymer composition of both filler layers is (a) crosslinked polyolefin modified by grafting one or more unsaturated carboxylic acid anhydride to anhydride content 0.1-20 weight %; (b) polyhydric alcohol with at least two OH groups; and (c) reaction accelerator, where the mole ratio of (carboxylic acid anhydride units in (a)):(b) is 0.01-10:1, and weight ratio (a):(c) is 100:0.001-20. Or the (a) component is a copolymer which contains ethylene, 0.1-20 weight % of one or more radical-polymerizable carboxylic acid, and 30% or more of the comonomer. Or the resin composition consists of olefin resin modified by unsaturated carboxylic acid anhydride and unsaturated carboxylic acid ester, with an average of one or more carboxylic acid anhydride per molecule, and a ratio of ester to anhydride of 0.5-20; and a compound with one or more OH groups per molecule, with a ratio of OH groups in (b) to anhydride groups in (a) of 0.1-5. The solar battery element is made from crystalline or amorphous silicon. The backing protection sheet is made from metal sheet, metal foil, fluorinated resin, cyclic polyolefin, polycarbonate, poly(meth)acrylate, polyamide or polyester resin; or a multilayer sheet of two or more of these. The surface layer and/or the backing layer is laminated to the filler layer in advance. EXAMPLE - The thermoplastic crosslinked polyolefin resin for the filler layer was formed from a modified polyolefin composition with MFR 70g/10 minutes, breaking strength 310 kg/cm2 of polypropylene grafted with maleic anhydride (0.5 weight %). It was drawn at 40%. A mixture was prepared from 95 weight % of this resin, 0.2 weight % trimethylolpropane, 1 weight % ethylene -methacrylate resin (18% methacrylate, 10 % of methacrylate neutralized by sodium: MFR 3.0g/10 minutes, density 0.94 g/cm3) and 0.1 % weight % of 2,6-di-t-butyl-p-cresol oxidation inhibitor (N.B. total less than 100%). It was melt-mixed at 250degreesC. The module was prepared by laminating a 3mm glass sheet, a 400 micron thick film of the filler material, amorphous silicon solar battery elements arranged in parallel on a biaxially oriented polyethylene terephthalate film 38 microns thick, another 400 micron thick film of the filler material, and a 50 micron thick biaxially oriented polyethylene terephthalate film, using an adhesive layer of acrylate resin between each layer.