SrTiO₃ recombination-inhibiting barrier layer for type II dye-sensitized solar cells

Type II dye-sensitized solar cells (DSSCs) differ from conventional DSSCs by their mechanism of light absorption and electron injection. Instead of photoexcitation of the dye, followed by electron injection to the semiconductor conduction band, in type II DSSCs, there is a direct electron injection from the HOMO level of the sensitizer into the conduction band of the semiconductor. The main drawback of such cells is their extremely rapid back-electron-transfer rate. Herein, we present a new approach for inhibiting back electron transfer in a catechol-sensitized type II DSSC using a thin layer barrier coating of SrTiO₃ between the semiconductor and the sensitizer. A 70% improvement in charge collection efficiency is reported. A proposed mechanism for the operation of the SrTiO₃ barrier layer is presented.