Precise modification of the interface between titanium dioxide and electrolyte of dye-sensitized solar cells with oxides deposited by thermal evaporation of metals and subsequent oxidation

This manuscript reports the modification of the interface between the mesoporous TiO2 work electrode and electrolyte of dye-sensitized solar cells (DSCs) with oxide layers deposited by the thermal evaporation of metals and subsequent oxidation with UV ozone. Both Al2O3 and MgO can be deposited on mesoporous TiO2 by this method, and their thickness can be precisely controlled. A thin layer of Al2O3 or MgO on the TiO2 work electrode can improve the photovoltaic efficiency. The optimal thicknesses are 14.1 and 4.9 Å for Al2O3 and MgO, respectively. The oxide effect has been investigated by the electrochemical impedance spectroscopy, cyclic voltammetry and UV–Vis–NIR absorption spectroscopy. The improvement in the photovoltaic efficiency by an oxide layer is attributed to the upward shift of the conduction band of TiO2, the passivation of the TiO2 surface, and the retardation of the charge recombination through the interface between TiO2 and electrolyte.

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► Al2O3 and MgO were coated by thermal evaporation of metals and subsequent oxidation.
► The thickness of the oxide layers can be precisely controlled.
► Oxide layers were coated on TiO2 of DSCs to modify its interface with electrolyte.
► The oxide layers remarkably improve the photovoltaic performance of DSCs.