A solar cell module comprising a solar cell layer and an ionomer sheet, wherein, the solar cell layer comprises a single solar cell or a plurality of electrically interconnected solar cells and optionally has a front sun-facing side and a back non-sun-facing side and; the ionomer sheet comprises a sodium/zinc mixed ionomer that is the neutralization product of a precursor acid copolymer; wherein the precursor acid copolymer comprises copolymerized units of an α-olefin having 2 to 10 carbon atoms and 20 to 30 wt%, of copolymerized units of an α,β-ethylenically unsaturated carboxylic acid having 3 to 8 carbon atoms, based on the total weight of the precursor acid copolymer; wherein the precursor acid copolymer has a melt flow rate of 70 to 1000 g/10 min, as determined in accordance with ASTM D1238 at 190°C and 2.16 kg; and wherein said precursor acid copolymer, when neutralized to a level of 40% to 90%, based on the total number of the carboxylic acid groups present in the precursor acid copolymer, to comprise carboxylate groups and counterions that consist essentially of sodium ions, produces a sodium ionomer, said sodium ionomer having a freeze enthalpy that is not detectable (less than 0.2 J/g) or that is less than 3.0 J/g, when determined by differential scanning calorimetry in accordance with ASTM D3418; and wherein said sodium/zinc mixed ionomer comprises carboxylate groups and a mixture of counterions; said mixture of counterions consisting of 5 to 95 equivalent%, of sodium cations, and, complementarily, 5 to 95 equivalent%, of zinc cations, based on the total number of equivalents of carboxylate groups in the precursor acid copolymer. the solar cell layer comprises a single solar cell or a plurality of electrically interconnected solar cells and optionally has a front sun-facing side and a back non-sun-facing side and; the ionomer sheet comprises a sodium/zinc mixed ionomer that is the neutralization product of a precursor acid copolymer; wherein the precursor acid copolymer comprises copolymerized units of an α-olefin having 2 to 10 carbon atoms and 20 to 30 wt%, of copolymerized units of an α,β-ethylenically unsaturated carboxylic acid having 3 to 8 carbon atoms, based on the total weight of the precursor acid copolymer; wherein the precursor acid copolymer has a melt flow rate of 70 to 1000 g/10 min, as determined in accordance with ASTM D1238 at 190°C and 2.16 kg; and wherein said precursor acid copolymer, when neutralized to a level of 40% to 90%, based on the total number of the carboxylic acid groups present in the precursor acid copolymer, to comprise carboxylate groups and counterions that consist essentially of sodium ions, produces a sodium ionomer, said sodium ionomer having a freeze enthalpy that is not detectable (less than 0.2 J/g) or that is less than 3.0 J/g, when determined by differential scanning calorimetry in accordance with ASTM D3418; and wherein said sodium/zinc mixed ionomer comprises carboxylate groups and a mixture of counterions; said mixture of counterions consisting of 5 to 95 equivalent%, of sodium cations, and, complementarily, 5 to 95 equivalent%, of zinc cations, based on the total number of equivalents of carboxylate groups in the precursor acid copolymer.