Rare‐earth and Nb doping of TiO 2 nanocrystalline mesoscopic layers for high‐efficiency dye‐sensitized solar cells

The improvement of dye‐sensitized solar cells (DSSCs) performance can be realized by using rare‐earth and Nb‐doped TiO 2 mesoporous photoelectrodes. The undoped, Nb‐doped, and rare‐earth‐doped TiO 2 mesoscopic layers were prepared using a sol–gel method followed by a hydrothermal treatment. The Nb content was varied from 0.7 to 2.7 mol.%. The samples of complex rare‐earth titanium oxides with fluorite‐like structure containing Nb were synthesized using mechanical activation method. A series of fluorite‐like Sm 2 [Ti x Nb 1– x ] 2 O 7 compounds with varied Nb content was synthesized. The structure and morphology of obtained materials were characterized using XRD, SEM, and optical absorption spectroscopy. The prepared TiO 2 mesoscopic layers were used for fabrication DSSCs. We have found that the photovoltaic parameters of DSSCs based on TiO 2 sensitized with N719 dye, are closely related to the electronic structure of the Nb‐doped TiO 2 electrodes. The changes of short circuit current of DSSCs were explained in relation to the electronic structure of the TiO 2 electrodes. We have shown that the Nb doping enhances the junctions between neighboring nanoparticles and decreases the bulk electrical resistivity of the TiO 2 electrodes. For the TiO 2 electrodes doped with Nb the best DSSC performance with the energy conversion efficiency of 9.7% was obtained for Ti 0.983 Nb 0.017 O 2 compound with 1.7 mol.% of Nb. Thus we have improved the device efficiency by 9% in comparison with the DSSC based on undoped TiO 2 electrode. The developed rare‐earth doped compounds SmTiNbO were also used for fabrication and characterization of DSSCs. However, unlike Nb‐doped TiO 2 layers, the efficiencies of DSSCs based on Nb‐doped complex rare‐earth titanium oxides were low in comparison with undoped TiO 2 .