Results are presented for the microstructure of alpha -Si : H solar cells grown on metallized polymer substrates. The structures studied were Kapton/metal/n-i-p alpha -Si : H/ZnO, where silver and aluminum were used as the metal back contacts. The alpha -Si : was deposited at temperatures ranging from 100-200 degreesC. A second identical range of cells, except for the insertion of an 80 nm thick ZnO buffer-layer between the metal and n-layer, was also studied. A range of measurements utilising scanning electron microscopy, energy dispersive x-ray spectroscopy, Raman scattering and X-ray diffraction were made on the samples to determine the material properties. It is demonstrated that the surface morphology and microstructure of these cells are strongly dependent on the substrate temperature during deposition of the alpha -Si : H, choice of back contact metal, and the ZnO buffer-layer. It is argued that the material properties of cells grown on flexible metallized substrates differ from those grown on conventional TCO covered glass substrates.