Polyiodide Hybrid Perovskites: A Strategy To Convert Intrinsic 2D Systems into 3D Photovoltaic Materials

Two new organic–inorganic hybrid perovskite compounds, (Me3S)2Pb5I14*2I2 (1) and (C8H11S)2Pb2I6*I2 (2), have been synthesized and subsequently characterized in this study. The materials were synthesized from facile one-pot, one-step reactions of lead iodide, corresponding sulfide, methanol, iodine, and hydroiodic acid in the case of 2. Structural analysis reveals the presence of polyiodide entities in both compounds. Compound 1 contains triiodide anions, I3–, that are uniquely shared between the 2D inorganic slabs, forming a 3D network. Both 1 and 2 have I2 molecules that are bridging the inorganic slabs through a structural motif that can be regarded as a tetraiodide anion, I42–. Optical spectroscopy shows band gaps of 1.86 eV for 1 and 1.89 eV for 2. The optoelectronic properties were further investigated with band structure calculations. Single-crystal IV-characteristics of 1 show that the compound is photoactive confirming it as a promising photovoltaic candidate. Compound 1 highlights a novel strategy of designing 3D semiconducting hybrid materials by incorporating polyiodides to provide direct geometric and electronic connections between the semiconducting inorganic perovskite sheets.