Solar cell modules comprising encapsulant sheets with low haze and high moisture resistance

A solar cell module comprising a solar cell layer and an ionomer sheet, wherein,

• (A) the solar cell layer comprises a single solar cell or a plurality of electrically interconnected solar cells and;
• (B) 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 about 20 to about 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 about 70 to about 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 about 40% to about 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 or that is less than about 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 essentially of about 5 to about 95 equivalent % of sodium cations, and, complementarily, about 95 to 5 equivalent % of zinc cations, based on the total number of equivalents of carboxylate groups in the precursor acid copolymer.