Solar cells with high short circuit currents based on CsPbBr3 perovskite-modified ZnO nanorod composites

3-D all-inorganic perovskite solar cells have been built using vertically aligned conductive zinc oxide nanorods as the electron transport layer and optical waveguide. Yttrium doping improved the conductivity and hence the electron transportation of the ZnO achieving a threefold improvement of the solar cell efficiency. The vertically aligned nanorods act as optical waveguides and a scaffold, which improved photoabsorption of the perovskite semiconductor by increasing layer thickness. Our device structure was completed with an exfoliated multilayer graphite back contact for effective hole-extraction. The ZnO was most significantly modified by nanometre scale coatings of TiO2 in order to passivate the surface and reduce charge recombination, as measured by photoluminescence spectroscopy. This led to greatly improved charge transfer. This strategy led to an overall nine times enhancement in the solar cell efficiency, yielding a competitive top value of 5.83%. More importantly, the all-inorganic solar cells demonstrated excellent stability, showing no decline in initial performance after 1000 hour storage in ambient conditions. This work presents yttrium doped ZnO nanorods as a suitable replacement for mesoporous TiO2, achieving a high short circuit current of 10.5 mA cm-2 for CsPbBr3 perovskite devices.