Colloidal cadmium selenide (CdSe) quantum dots QDs) have been prepared and exploited as inorganic dyes to sensitize a large-band-gap TiO2 layer for QD-sensitized solar cells. The optimized QD-sensitized solar cells exhibited an unprecedented incident photon-to-charge carrier generation efficiency of 36% and an overall conversion efficiency of over 1.7% at 0.1 sun and 1% at full sun intensity with a cobalt(II/III)-based redox system. The photovoltaic characteristics of CdSe QD-sensitized cells are compared with standard dye-sensitized solar cells, in which the former exhibited about half of the efficiency of the latter. From the kinetics of charge transfer monitored using transient spectroscopic and voltage decay measurements in the CdSe QD-sensitized cell, the regeneration yield of oxidized QDs was found to be close to almost unity, and the electron lifetime was longer in the CdSe QD-sensitized cell than in the dye-sensitized solar cell.