TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The acid copolymer comprises a finite amount of polymerized residues of alpha -olefin and polymerized residues of an alpha , beta -ethylenically unsaturated carboxylic acid ( greater than or equal to 1 wt.%). The ionomer is a derivative of a parent acid copolymer comprising a finite amount of polymerized residues of an alpha -olefin and polymerized residues of an alpha , beta -ethylenically unsaturated carboxylic acid ( greater than or equal to 10 wt.%), based on a total weight of the parent acid copolymer and having 10-100% of a total carboxylic acid content neutralized with metallic ions. The ethylene acrylate ester copolymer comprises a finite amount of polymerized residues of an alpha -olefin and polymerized residues of an acrylate ester ( greater than or equal to 1 wt.%). Preferred Film: At least one surface of the thermoplastic film or sheet is a rough surface. Preferred Assembly: The front-sheet encapsulant layer is formed of the one layer of the thermoplastic film or sheet (F1), and optional back-sheet encapsulant layer comprises a polymeric composition selected from poly(vinyl butyral), ionomer, ethylene vinyl acetate, acoustic poly(vinyl acetal), polyurethane, polyvinylchloride, polyethylene, polyolefin block elastomer, ethylene acrylate ester copolymer, acid copolymer, silicone elastomer and epoxy resin. The back-sheet encapsulant layer is formed of a second layer of the thermoplastic film or sheet. The assembly (A1) further comprises an incident layer that is formed of a transparent material and serves as an outer layer at the light-receiving side of the assembly, where the transparent material is glass or a plastic film or sheet; or a backing layer that serves as an outer layer at the back side of the assembly, where the backing layer is formed of glass, plastic sheets or films, or metal sheets or films. In the assembly (A2), the incident layer is formed of glass and the front-sheet encapsulant layer is formed of the one layer of the thermoplastic film or sheet (F1) and having its first ionomeric or acid copolymeric surface layer adjacent and in direct contact with the glass incident layer. The backing layer is also formed of glass and the back-sheet encapsulant layer is formed of a second layer of the thermoplastic film or sheet (F1) and having its first ionomeric or acid copolymeric surface layer adjacent and in direct contact with the glass backing layer. Preferred Cells: The solar cells are selected from multi-crystalline solar cells, thin film solar cells, compound semiconductor solar cells, and amorphous silicon solar cells.