Pb6Ba3Si2S8I10: A new thiohalide with a quasi-two-dimensional structure and wide band gap

Abstract

Pb-based chalcogenides display abundant structure diversity and distinguished properties. Based on a mixed anion and dimensional reduction combined strategy, a wide band gap Pb-based thiohalide, Pb6Ba3Si2S8I10, has been rationally designed and fabricated in the experiment by the flux method. The compound crystallizes in Rc space group with cell parameters a = 9.7925(2) Å, b = 9.7925(2) Å, c = 70.628(3) Å, and is composed of [SiS4] tetrahedra and unprecedented [PbI5S2] polyhedral units, resulting a unique quasi-two-dimensional structure, which enriches the chemical and structural diversity of Pb-based thiohalides. The experimental band gap of Pb6Ba3Si2S8I10 was measured to 2.80 eV. Based on statistical analyses, and to the best of our knowledge, it is the largest experimental optical band gap in the known Pb-based thiohalides. The results demonstrate the feasibility of highly electropositive Ba atom in regulating the dimension of structural framework of thiohalides, and give new insights into the structure and property modifications of thiohalides by the mixed anion and dimensional reduction combined strategy.