New Lead-Halide-Based Organic-Inorganic Hybrids: Syntheses, Crystal Structures and Optical Properties

New lead-halide-based organic-inorganic hybrid compounds were synthesized in solution. Crystal structures of intermediate phases during perovskite CH3NH3PbI3 thin-film deposition were determined for the first time. The ribbon-like inorganic framework was derived from PbI2 layer and solvent molecules of DMSO or DMF were discovered to be involved in the crystal structure. After annealing, structural solvent molecules were removed and the inorganic network underwent a rearrangement to a perovskite structure. A series of diamine-based triple-layered perovskites H3N(CH2)XNH32Pb3I10 (X = 6, 7, 8 and 9) were synthesized and fabricated into photovoltaic devices. The crystal structures were determined by single crystal and powder X-ray diffraction. Thin films of the series displayed strong preferred orientation, indicating a film growth along (110) crystallographic plane. The 2D hybrid perovskites were used as light absorbers in planar heterojunction solar cell that exhibited power-conversion efficiencies of up to 8.85%. Another group of new 2D non-perovskite hybrids were synthesized with different organic cations. The crystal structures involve various connectivity modes of coordination polyhedra, including corner-, edge-, face-sharing, and mixed connectivity modes. The optical band gaps were evaluated by absorption and photoluminescence spectra and structure-optical band gap relationship was explored based on different connectivity configurations and metal-metal distance. In the last section, lead(II) complexes with ligands derived from cleavage of 1,2,4,5-tetrazine ring were synthesized under different conditions. A ring-opening process with two-electron reduction was observed in one of the complexes, resulting in a negatively charged bridging ligand.