A photovoltaic cell comprising a transparent front-plane, an opaque back-plane and an encapsulant resin wherein said back-plane comprises a polyester film comprising a base layer (B) comprising a crystallizable polyester and a heat-sealable layer (A) comprising an amorphous copolyester wherein: (i) said amorphous copolyester is derived from an aliphatic diol and a cycloaliphatic diol and at least one aromatic dicarboxylic acid (ii) said polyester film is disposed in the photovoltaic cell such that layer (A) is in contact with the encapsulant resin.