NOVELTY - The backsheet (100) comprises a first exterior layer (101), and 2 wt. percentage of a second exterior polymer (103), where the first exterior layer has a residual fusion heat after lamination at 150 degree C of 50 J/g. The first exterior layer comprises 35 wt. percentage of thermoplastic olefin polymer including polypropylene, polymethylpentene and ethylene vinyl alcohol copolymer, preferably polypropylene. The second exterior layer is formed on opposite side of the first exterior layer and co-extruded with the first exterior layer. The thermoplastic olefin polymer is present in each additional layer of the backsheet.    USE - The backsheet is useful in a photovoltaic module (claimed).    ADVANTAGE - The inexpensive backsheet has favorable performance at high operating temperatures, and does not have high water vapor transmission rate.    DETAILED DESCRIPTION - The backsheet (100) comprises a first exterior layer (101), and 2 wt. percentage of a second exterior polymer (103), where the first exterior layer has a residual fusion heat after lamination at 150 degree C of 50 J/g. The first exterior layer comprises 35 wt. percentage of thermoplastic olefin polymer consisting of polypropylene, polymethylpentene and ethylene vinyl alcohol copolymer, preferably polypropylene. The second exterior layer is formed on opposite side of the first exterior layer, and is co-extruded with the first exterior layer. The thermoplastic olefin polymer is present in each additional layer of the backsheet, such that the backsheet layers are chemically affinitive. A first interior layer (102) is used to bond the first exterior layer to the second exterior layer, and has thickness of 20-100 milli meter. The first exterior layer has a bonding adhesion to ethylene vinyl acrylate of greater than 40 N/cm after lamination to the ethylene vinyl acrylate at 140-150 degree C. An INDEPENDENT CLAIM is included for a method for manufacturing a layer in a backsheet for a photovoltaic module.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a backsheet.    Backsheet (100)    First exterior layer (101)    First interior layer (102)    Second exterior layer. (103)