Lead-Doped Titanium-Oxo Clusters as Molecular Models of Perovskite-Type PbTiO3 and Electron-Transport Material in Solar Cells
Graphical Outstanding resemblance ! The first molecular model of perovskite PbTiO 3 has been successfully prepared by bottom-up assembly of lead-doped titanium-oxo clusters in the presence of p - tert -butylthiacalix[4]arene as stabilizing ligands. Structural characterization confirmed that the clusters have almost the same structure as that in PbTiO 3 (see figure). The nanoclusters showed high solution stability and can be applied as electron-transport materials in perovskite solar cells to give satisfactory efficiencies and high device stability. In this work we have successfully prepared two lead-doped titanium-oxo clusters with core structures that resemble isolated perovskite PbTiO 3 species. In the obtained highly symmetric Pb 8 Ti 7 -oxo cluster, the central TiO 6 octahedra are orthogonally extended to adjacent octahedra through corner-sharing and the eight dopant lead ions form a cubic arrangement, making it the first molecular model of perovskite PbTiO 3 . Moreover, the clusters readily dissolved in chloroform and showed high solution stability, as confirmed by MALDI-TOF MS measurements. Based on such solution processability, they can be easily spin-coated to form homogeneous films, which were employed as electron-transport materials in perovskite solar cells to give an average power conversion efficiency of around 15 % and improved device stability. This newly developed bottom-up cluster assembly method provides an efficient approach to the construction of atomically precise models of perovskite metal oxides as well as potential molecular tools to extend their applications.
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