NOVELTY - Obtaining a heat pressed multi-layer fluoropolymer film or sheet that has improved bonding strength to a polyolefin film, comprises: (i) providing a multi-layer fluoropolymer film or sheet comprising a first oriented fluoropolymer film or sheet layer that is laminated to an oriented polyester film or sheet layer; and (ii) heat pressing the multi-layer fluoropolymer film or sheet by a heat press means, where the heat press means is set at such conditions that the multi-layer fluoropolymer film or sheet receives a pressure of 0.01-50 Kgf/cm2 and a heat of 150 degrees C-260 degrees C.    USE - The method is useful for obtaining heat pressed multi-layer fluoropolymer film or sheet that has improved bonding strength to polyolefin film (claimed).    ADVANTAGE - The multi-layer fluoropolymer film or sheet has improved adhesion to other polymeric material.    DETAILED DESCRIPTION - Obtaining a heat pressed multi-layer fluoropolymer film or sheet that has improved bonding strength to a polyolefin film, comprises: (i) providing a multi-layer fluoropolymer film or sheet comprising a first oriented fluoropolymer film or sheet layer that is laminated to an oriented polyester film or sheet layer, where the first oriented fluoropolymer film or sheet layer consists essentially of fluoropolymer and the oriented polyester film or sheet layer consists essentially of polyester, and where the first oriented fluoropolymer film or sheet layer provides one of the two opposite outer surface layers of the multi-layer fluoropolymer film or sheet; and (ii) heat pressing the multi-layer fluoropolymer film or sheet by a heat press means, where the heat press means is set at such conditions that the multi-layer fluoropolymer film or sheet receives a pressure of 0.01 -50 Kgf/cm2 and a heat of 150 degrees C-260 degrees C. INDEPENDENT CLAIMS are:    (1) a heat pressed multi-layer fluoropolymer film or sheet prepared by the method; and    (2) a solar cell module comprising one or more solar cells, a back encapsulant sheet laminated to a back side of the solar cells, and a backsheet laminated to a back side of the back encapsulant sheet, where the back encapsulant sheet comprises a polyolefin, and where the backsheet is formed of the heat pressed multi-layer fluoropolymer film or sheet.