MgCl2 passivated ZnO electron transporting layer to improve PbS quantum dot solar cells

The unique tunable bandgaps and straightforward synthesis of colloidal quantum dots make them promising low-cost materials for photovoltaics. High-performance colloidal quantum dot solar cells rely on good-quality electron transporting layers to make carrier selective contacts. Despite extensive use of n-type oxides as electron transporting layers, a detailed understanding of their surface and interface states as well as mechanisms to improve their optical properties are still under development. Here, we report a simple procedure to produce MgCllsubg2l/subg passivated ZnO nanoparticles electron transporting layers that show improved device performance. The MgCllsubg2l/subg treated ZnO electron transporting layers boost the PbS colloidal quantum dot cell efficiency from 6.3% to 8.2%. The cell exhibits reduced defects leading to significant improvements of both FF and Jlsubgscl/subg. This low-temperature MgCllsubg2l/subg treated ZnO electron transporting layer may be applied in solution processed tandem cells as a promising strategy to further increase cell efficiencies.