NOVELTY - A multi-layer photovoltaic module backsheet (10) combining low lateral flow and excellent release properties comprises: UV stabilized flexible polypropylene main layer (11), where its polymeric part has residual heat of fusion at lamination temperature of more than 10 (preferably more than 20) J/g; coextruded layer (13) facing cells on base of thermoplastic polyolefin polymer blend which has residual heat of fusion at lamination temperature of less than 10 (preferably less than 3) J/g, preferably at melted temperature.    USE - In photovoltaic module, as integrated insulation layer on a metallic or a metal/polymer composite substrate (claimed).    ADVANTAGE - The backsheet has a cold foldability of lower than -20 (preferably lower than -40) degrees C. The backsheet shows reliable adhesion with peroxide crosslinkable ethylene vinyl acetate (EVA) back adhesive layer, barrier properties, enough dimensional stability, improved mechanical properties retention (integrity) and limited heat distortion (flow) at usual vacuum lamination process, excellent aging (no hydrolysis), excellent electrical properties (greater than 1000 direct-current voltage (VDC) partial discharge voltage), excellent cold temperature mechanical properties and weldability to junction boxes. The material composition of the backsheet layer facing the active layer, controls the coupling reactions triggered by the peroxides and silanes of the crosslinkable EVA back adhesive layer, thus provides improved mechanical properties of and more reliable adhesion between backsheet and crosslinkable EVA adhesive layer.    DETAILED DESCRIPTION - A multi-layer photovoltaic (PV) module backsheet (10) combining low lateral flow and excellent release properties comprises: UV stabilized flexible polypropylene (FPP) main layer (11), where its polymeric part has a residual heat of fusion at lamination temperature of more than 10 (preferably more than 20) J/g; at least one coextruded layer (13) facing the cells on base of thermoplastic polyolefin (TPO) polymer blend which has a residual heat of fusion at lamination temperature of less than 10 (preferably less than 3) J/g, preferably at melted temperature, where the backsheet has a cold foldability of lower than -20 (preferably lower than -40) degrees C. INDEPENDENT CLAIMS are included for the following:    (1) a PV module comprising the backsheet; and    (2) use of chemical vapor deposition (CVD), physical vapor deposition (PVD) (reactive sputtering), atmospheric plasma or amino-silane wet coating to improve the adhesion of top layer (1), or cells with functional PO tie-layers or with functionalized TPO surfaces.    DESCRIPTION OF DRAWING(S) - The figure shows cross section of a photovoltaic module with a coextruded or colaminated flexible polypropylene backsheet.    Top layer (1)    Upper adhesive layer (2)    Ethylene vinyl acetate adhesive layer (5)    Photovoltaic module backsheet (10)    Flexible polypropylene main layer (11)    Coextruded layer (13)