The study of the treatment of cerium-zinc sulfide passivation layer on photovoltaic performance of CdSe0.2S0.8 ternary quantum dot sensitized solar cells

Abstract

The strategy of surface passivation layer in the quantum dot sensitized solar cells (QDSSCs) is one of the efficient methods of preventing surface charge recombination and, accordingly, enhancing the power conversion efficiency (PCE). In this work, some metal ions (M) (including: Mg2+, Sr2+, Al3+, Sn4+, Cr2+, La3+ and Ce3+)-doped ZnS passivation layer have been inserted at the interface between TiO2 and CdSexS1-x (Se:S = 1:4)/ZnS QDs to prepare a novel TiO2/M-ZnS/CdSe0.2S0.8 (simplified as CdSeS)/ZnS photoelectrode. The effects of this inner layer on the photovoltaic characteristics of the TiO2/CdSeS/ZnS QDSSCs were systematically investigated. The results of photovoltaic measurement show that among different M−ZnS ternary layers, the introduction of Ce–ZnS layer is the best choice for the surface passivation of TiO2 film. Finally, 15% Ce-doped ZnS yielded a high PCE of 5.15% with an increase of more than 28% of efficiency compared to those of CdSeS cells without this inner layer (TiO2/CdSeS/ZnS). Our studies indicated that the Ce–ZnS layer acts as both an effective passivation layer and a seed layer which not only reduces the surface charge recombination, but also enhances the visible light absorption capability, the lifetime and the collection of photoelectrons in the TiO2 film of the Ce–ZnS/CdSeS/ZnS QDSSCs.