ZnO nanowalls grown at low-temperature for electron collection in high-efficiency perovskite solar cells

• ZnO nanowall used as an ECL for CH3NH3PbI3 perovskite solar cells.
• ZnO nanowalls were grown by CBD method using a Al film layer.
• The conversion efficiency at AM1.5G illumination was 13.6%.

This paper reports on the fabrication of ZnO nanowalls for use as an electron collecting layer (ECL) in CH3NH3PbI3 perovskite solar cells (PSCs). Two-dimension ZnO nanowalls were grown using a low-temperature chemical bath method with a thin Al film as a seed layer. We compared electron collecting layers based on nanowalls and sol–gel derived ZnO thin film in PSCs and sought to identify the mechanism underlying the collection of electrons. The proposed ZnO nanowalls achieved a fill factor significantly higher than that of ZnO thin films, which translated into a remarkable improvement in power conversion efficiency, reaching 13.6% under AM 1.5G illumination.