Much attention has been paid to the development of dye-sensitized solar cells (DSCs) owing to a possibility of low production cost. One of the main factors that has hampered the practical application of DSCs is the use of a transparent conducting oxide (TCO) substrate of very high cost. Here we introduce a newly structured DSC back contact dye-sensitized solar cell (BCDSC) in which the TCO is omitted and a porous Ti electrode for electron collection, called a back contact electrode (BCE), is placed on the side opposite to the side of light irradiation. We succeeded in fabricating on the TiO2 film a BCE with large enough pore size for both efficient dye adsorption onto the film and smooth I−/I3− redox couple transportation through the film. Electrochemical impedance spectroscopy study showed that increase in the BCE thickness causes increase in the I−/I3− redox couple transport resistance at the same time as reduction of BCE resistance. Under standard air mass (AM) 1.5 irradiation (100 mW cm−2), a BCDSC wi...