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ZnO thin films having a nanocolumnar microstructure are grown by plasma-enhanced chemical vapor deposition at 423 K on pre-treated fluorine-doped tin oxide (FTO) substrates. The films consist of c-axis-oriented wurtzite ZnO nanocolumns with well-defined microstructure and crystallinity. By sensitizing CH3NH3PbI3 on these photoanodes a power conversion of 4.8% is obtained for solid-state solar cells. Poly(triarylamine) is found to be less effective when used as the hole-transport material, compared to 2,2,7,7-tetrakis(N,N-di-p-methoxyphenylamine)-9,9-spirobifluorene (spiro-OMeTAD), while the higher annealing temperature of the perovskite leads to a better infiltration in the nanocolumnar structure and an enhancement of the cell efficiency.

Advanced energy materials 10(2), 1901524 (2020). doi:10.1002/aenm.201901524, The main handicap still hindering the eventual exploitation of organometal halide perovskite���based solar cells is their poor stability under prolonged illumination, ambient conditions, and increased temperatures. This article shows for the first time the vacuum processing of the most widely used solid���state hole conductor (SSHC), i.e., the Spiro���OMeTAD [2,2���,7,7������tetrakis (N,N���di���p���methoxyphenyl���amine) 9,9������spirobifluorene], and how its dopant���free crystalline formation unprecedently improves perovskite solar cell (PSC) stability under continuous illumination by about two orders of magnitude with respect to the solution���processed reference and after annealing in air up to 200 ��C. It is demonstrated that the control over the temperature of the samples during the vacuum deposition enhances the crystallinity of the SSHC, obtaining a preferential orientation along the ������� stacking direction. These results may represent a milestone toward the full vacuum processing of hybrid organic halide PSCs as well as light���emitting diodes, with promising impacts on the development of durable devices. The microstructure, purity, and crystallinity of the vacuum sublimated Spiro���OMeTAD layers are fully elucidated by applying an unparalleled set of complementary characterization techniques, including scanning electron microscopy, X���ray diffraction, grazing���incidence small���angle X���ray scattering and grazing���incidence wide���angle X���ray scattering, X���ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy., Published by Wiley-VCH, Weinheim