Abstract
We report here on the crystal structure and physical properties of ((CH3)3S)2SnX6 (X = Cl, Br, I) compounds as well as the application of ((CH3)3S)2SnI6 in dye-sensitized solar cells. Powder X-ray diffraction and Rietveld analysis show that the materials form a cubic structure with a 0D network of [SnX6] octahedra, which can be considered as a defect variant (AB0.5X3) of the perovskite archetype (ABX3). The electronic band gaps of ((CH3)3S)2SnX6 were determined by UV–Vis reflectance spectroscopy at 4.1, 2.9 and 1.4 eV for X = Cl, Br, and I, respectively. The direct bandgap and its relative decrease in the order of light to heavy halide was independently verified by density-of-states calculations. According to Raman spectroscopy, the lattice vibrations also depend largely on the halogen atom. The air-stable and non-toxic ((CH3)3S)2SnI6 compound was incorporated in electrolyte-free, dye-sensitized solar cells based on the Z907 chromophore chemisorbed onto mesoporous titania electrodes. A power conversion efficiency of 5% is achieved for these photovoltaic devices, confirming efficient charge transport in the bulk ((CH3)3S)2SnI6 and hole extraction at the perovskite-Pt interface.
Published Version
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