Highly efficient dye-sensitized solar cells (similar to 8.6%) using a flexible stainless steel substrate for preparation of a mesoporous TiO2 film electrode were fabricated by controlling the dark current density. Optimal photovoltaic properties were obtained with a cell where the TiO2 film was coated on a Ti-isopropoxide-treated stainless steel-based substrate. The quality of the underlayer was characterized and found to be related with the photovoltaic properties. (c) 2008 The Electrochemical Society.