Lead methylammonium triiodide perovskite-based solar cells: An interfacial charge-transfer investigation

This work reports on an investigation into interfacial charge transfer in CH₃NH₃PbI₃ perovskite solar cells by using anatase TiO₂ nanocuboids enclosed by active {100} and {001} facets. The devices show 6.0 and 8.0% power conversion efficiency with and without hole-transport material. Transient photovoltage/photocurrent decay and charge extraction, as well as impedance spectroscopy measurements, reveal that carbon materials are effective counter electrodes in perovskite solar cells. The photogenerated charges are observed to be stored in mesoporous TiO₂ film under illumination and in the CH₃NH₃PbI₃ layer in the dark. The use of 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9-spirobifluorene (spiro-MeOTAD) as a hole-transport material accelerates interfacial charge recombination between the photogenerated electrons and holes.