Improve the performance of the quantum dot sensitized ZnO nanotube solar cells with inserting ZnS-MnS composites layers

Interface passivation layer deposited onto photoanodes has been proven to be an available way to suppress charge recombination and enhance the power conversion efficiency in quantum dot-sensitized solar cells. In this work, the ZnS-MnS composites layers inserted in ZnO/CdS nanotubes photoanodes interface is firstly fabricated via ion-exchange and chemical bath deposition methods, simultaneously. By inserting the ZnS-MnS composites, electron back transfer is efficiently hindered. In addition, the uniform ZnS-MnS layer effectively blocks the direct contact between the polysulfide electrolyte and ZnO nanotubes, which inhabits the recombination of electron-hole pairs occurred at the interface. Besides, the MnS layer is in favour of the CdS quantum dots in higher load, profiting the light absorption intensity in the visible light region. Thus ZnO/ZnS-MnS/CdS nanotubes quantum dot-sensitized solar cells have efficiency of 3.62%, which is much higher than that of the solar cell with ZnS passivation layer (2.33%). This work demonstrates that constructing ZnS-MnS interface passivation layer with a proper band gap structure is a promising approach to enhance the performance of quantum dot-sensitized solar cells.