Synthesis, crystal structure and luminescence of [(CH₃)₃S]₂ZrCl₆

The current work reports on the synthesis, crystal structure and optoelectronic properties of (Me3S)2ZrCl6, prepared by reacting the solid precursors (Me3S)Cl and ZrCl4 in pyrex tubes at 150 °C under vacuum. According to X-ray powder diffraction and Rietveld analysis, (Me3S)2ZrCl6 crystallizes in the cubic space group Pa-3 (No. 205) with a = 12.4664(1) Å. The crystal structure consists of isolated trigonal pyramidal trimethylsulfonium cations and octahedral [ZrCl6]2- anions with weak hydrogen bonds among them and no signs of structural disorder. This 0D-material is stable in air and dissolves in water and dimethylformamide. Raman spectroscopy shows characteristic vibrational modes for the organic and inorganic moieties over the frequency range of 5–3200 cm−1. UV-Vis spectroscopy reveals a large band gap of 5.1 eV and a broadband luminescence with emission maximum at 465 nm in the solid state. The luminescent properties of (Me3S)2ZrCl6 are discussed and compared with those of similar inorganic or metal-organic compounds.</p

Optical-Vibrational Properties of the Cs₂SnX₆ (X = Cl, Br, I) Defect Perovskites and Hole-Transport Efficiency in Dye-Sensitized Solar Cells

We report the vibrational and optical properties of the ‘defect’ perovskites Cs₂SnX₆ (X = Cl, Br, I) as well as their use as hole-transporting materials (HTMs) in solar cells. All three air-stable compounds were characterized using powder X-ray diffraction and Rietveld refinement. Far-IR reflectance, Raman, and UV–vis spectroscopy as well as electronic band structure calculations show that the compounds are direct band gap semiconductors with a pronounced effect of the halogen atom on the size of the energy gap and the vibrational frequencies. Scanning electron microscopy and atomic force microscopy confirmed that the morphology of the perovskite films deposited from <i>N</i>,<i>N</i>-dimethylformamide solutions on TiO₂ substrates also strongly depends on the chemical composition of the materials. The Cs₂SnX₆ perovskites were introduced as hole-transporting materials in dye-sensitized solar cells, based on mesoporous titania electrodes sensitized with various organic and metal–organic dyes. The solar cells based on Cs₂SnI₆ HTM and the Z907 dye performed best with a maximum power conversion efficiency of 4.23% at 1 sun illumination. The higher performance of Cs₂SnI₆ is attributed to efficient charge transport in the bulk material and hole extraction at the perovskite-Pt interface, as evidenced by electrochemical impedance spectroscopy