This report presents a comparison of dye-sensitized solar cells based on nanocrystalline rutile and anatase forms of titanium dioxide (TiO₂). The objective of the study is to develop and optimize the new dye-sensitized solar cell technology. For the first time, crack-free nanocrystalline rutile TiO₂ films with thicknesses up to 12 micrometers were prepared and characterized. The photoelectrochemical properties of the rutile-based solar cell were compared with those of the conventional anatase-based cell. Intensity-modulated photocurrent spectroscopy and scanning electron microscopy studies indicate that electron transport is slower in the rutile layer than in the anatase layer due to differences in the extent of inter-particle connectivity associated with the particle packing density. The PV response of the dye-sensitized rutile-based solar cell is remarkably close to that of the anatase-based cell, despite the infancy of rutile material development for solar cells. Dye-sensitized solar cells based on nanocrystalline porous films of TiO₂ are a promising new kind of photovoltaic (PV) cell. These cells have demonstrated solar efficiencies of 10%–11% (AM1.5), stability of the semiconductor material, potentially inexpensive manufacturing and materials cost, use of environmentally friendly components, and potential unique applications (transparent, various possible colored dyes). The most extensively studied cell consists of a monolayer of a Ru-bipyridyl-based charge-transfer dye adsorbed onto the surface of a thin nanocrystalline TiO₂ film supported on transparent SnO₂ conducting glass. The particles of the film are in contact with an electrolyte solution containing iodide and triiodide ions as a redox relay and are sandwiched by a second plate of electrically conducting glass covered with platinum. The metal oxide is the recipient of injected electrons from optically excited dye molecules and provides the conductive pathway from the site of electron injection to the transparent back-contact. The redox species in solution transports the hole from the oxidized dye to the counter electrode, thus regenerating the original form of the dye and completing the oxidation-reduction cycle. The metal oxide can strongly influence the photovoltage, the fill factor, and the photon-to-current conversion efficiency (IPCE), which is determined by the light-harvesting efficiency of the dye, the quantum yield of electron injection, and the efficiency of collecting the injected electrons. Although most work on dye-sensitized nanocrystalline metal oxide solar cells has focused on the anatase form of TiO₂, rutile TiO₂ is potentially cheaper to produce and has superior light-scattering characteristics, which is a beneficial property from the perspective of effective light-harvesting.This report presents a comparison of dye-sensitized solar cells based on nanocrystalline rutile and anatase forms of titanium dioxide (TiO₂). The objective of the study is to develop and optimize the new dye-sensitized solar cell technology. For the first time, crack-free nanocrystalline rutile TiO₂ films with thicknesses up to 12 micrometers were prepared and characterized. The photoelectrochemical properties of the rutile-based solar cell were compared with those of the conventional anatase-based cell. Intensity-modulated photocurrent spectroscopy and scanning electron microscopy studies indicate that electron transport is slower in the rutile layer than in the anatase layer due to differences in the extent of inter-particle connectivity associated with the particle packing density. The PV response of the dye-sensitized rutile-based solar cell is remarkably close to that of the anatase-based cell, despite the infancy of rutile material development for solar cells. Dye-sensitized solar cells based on nanocrystalline porous films of TiO₂ are a promising new kind of photovoltaic (PV) cell. These cells have demonstrated solar efficiencies of 10%–11% (AM1.5), stability of the semiconductor material, potentially inexpensive manufacturing and materials cost, use of environmentally friendly components, and potential unique applications (transparent, various possible colored dyes). The most extensively studied cell consists of a monolayer of a Ru-bipyridyl-based charge-transfer dye adsorbed onto the surface of a thin nanocrystalline TiO₂ film supported on transparent SnO₂ conducting glass. The particles of the film are in contact with an electrolyte solution containing iodide and triiodide ions as a redox relay and are sandwiched by a second plate of electrically conducting glass covered with platinum. The metal oxide is the recipient of injected electrons from optically excited dye molecules and provides the conductive pathway from the site of electron injection to the transparent back-contact. The redox species in solution transports the hole from the oxidized dye to the counter electrode, thus regenerating the original form of the dye and completing the oxidation-reduction cycle. The metal oxide can strongly influence the photovoltage, the fill factor, and the photon-to-current conversion efficiency (IPCE), which is determined by the light-harvesting efficiency of the dye, the quantum yield of electron injection, and the efficiency of collecting the injected electrons. Although most work on dye-sensitized nanocrystalline metal oxide solar cells has focused on the anatase form of TiO₂, rutile TiO₂ is potentially cheaper to produce and has superior light-scattering characteristics, which is a beneficial property from the perspective of effective light-harvesting.