Minimizing the charge recombination rate at the FTO/Zn2SnO4 interface by metal oxide semiconductors in DSSCs
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Charge recombination at interfaces is one of the main factors that limit the power conversion efficiency of dye-sensitized solar cells. In this work, to reduce the charge recombination at the transparent conductive oxide/mesoporous Zn2SnO4 interface and then to improve the photovoltaic performance, different types of metal oxide semiconductor thin films (including SnO2, TiO2 and ZnO) are deposited on the FTO substrate by thermal evaporation method. The results reveal that in comparison with SnO2 and ZnO, the TiO2 dense layer acts as the most appropriate blocking layer for suppressing the charge recombination and increasing the short-circuit current density and power conversion efficiency of the fabricated device. Furthermore, because of the formation of energy barrier at the FTO/Zn2SnO4 interface, the charge recombination rate is minimized and the injected electrons from the excited dye molecules into the conduction band of Zn2SnO4 are accumulated in its conduction band which leads to upward shift of the Fermi level and increases open-circuit voltage. The maximum power conversion efficiency of 3.02% with short-circuit current density of 7.36 mA/cm2 and open-circuit voltage of 664 mV is obtained for the device comprising TiO2 blocking layer.
We gratefully acknowledge financial support from the Iran National Science Foundation (INSF), under Grant No. 95007269.
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