A highly efficient solar cell made from a dye-modified ZnO-covered TiO2 nanoporous electrode

A photoelectrochemical solar cell based on porous ZnO-covered TiO2 film has been fabricated with ruthenium bipyridyl complex as the sensitizer. The cell generated a short-circuit photocurrent of 21.3 mA cm(-2) and an open-circuit voltage of 712 mV under irradiation of 81.0 mW cm(-2) white light from a xenon lamp with an overall conversion efficiency of 9.8%. Compared with the pure TiO2 (anatase) film, the ZnO-covered TiO2 film possesses more outstanding ability to transport electrons with an overall power conversion efficiency increase by 27.3%. Optical electrochemical studies show that surface modification of TiO2 with ZnO can increase the concentration of free electrons in the conduction band of TiO2. This result implies that the charge recombination is reduced in the process of electron transport through the porous network, which can decrease the photocurrent loss and hence improve both short-circuit photocurrent and open-circuit photovoltage.