Molybdenum-coated hybrid polyimide composites as back contact layers for flexible solar cells

Molybdenum-coated polyimide films are excellent candidates to be used as flexible back contact layers in photovoltaic applications. In this work novel polymeric films consisting of filled polyimides containing mineral fillers (SiO2, sepiolite, Li and Na salts) have been prepared and used as substrates for the preparation of sputtered Mo thin films. A non-filled, i.e., as-prepared polyimide film, was additionally coated with Mo for comparison. The morphology and microstructure of the Mo films and their influence on the optical and electrical properties are studied as a function of the filler nature. A Mo film grown onto a non-filled polyimide film showed a low electrical resistivity (20 μΩ cm) and a high maximum optical reflectance of 93% (at λ=2250 nm). Mo films grown onto polyimides filled with fumed SiO2 and NaCl showed, by comparison, an improved reflectance of 99% and resistivities of 13 and 180 μΩ cm, respectively.