Hybrid Organic-Inorganic Halide Perovskite Single Crystals Directed By Phosphonium Cation-Templates

Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Dr. Ekkehard Sinn

Second Advisor

Dr. Sherine Obare

Third Advisor

Dr. Ramakrishna Guda

Fourth Advisor

Dr. Massood Atashbar


Hybrid halide perovskite, phosphonium-based perovskite, perovskite, perovskite single crystal, bulk low-dimensional perovskite (CBLDP), organic-inorganic perovskite single crystal


Inorganic/organic hybrid perovskites have emerged as synthetic materials that exhibit promising applications in optoelectronic devices. There is a wealth in choice of organic cations that can be used to create hybrid structures with different shape, size, polarizability, and electronegativity. Although perovskites with ammonium cations have been previously reported, a perovskite family with phosphonium cations has been less investigated. This study reports the synthesis, crystal, and characterization of the novel low-dimensional phosphonium-base organic-inorganic hybrid single crystal materials.

First, the phosphonium bromide salts were reacted with the lead bromides and iodides towards creating a perovskite crystal. Further reactions of phosphonium salts with the transition metal halides were made to discover if variant perovskite structures will be obtained. On the basis of the single-crystal X-ray diffraction results carried out at room temperature, the reaction of lead(II) bromide and iodide with various phosphonium salts produced a charge-balanced network of PbBr3 and PbI3– fragments connecting in a face-sharing octahedral motif. However, the reaction of lead(II) chloride and lead(II) iodide with tetraphenylphosphonium bromide (TPPB = C24H20PBr) produced a [Pb3(Cl/Br)8]2- and a [Pb2I6]2-that is surrounded by (C24H20P+) molecules (organic part), featuring a one-dimensional (1D) double chines and zero-dimensional (0D) structure, respectively. We note the increased cation size causes greater separation of charges, which tears apart the linked metal anion chains and lowers dimensionality; a separate effect was the formation of a new plumbate ion [Pb3(Cl/Br)8]2– where a Pb-phenyl interaction from a cation replaces an expected Pb-halogen bond.

These phosphonium-templated haloplumbates were found to possess semiconducting properties, as suggested by the results of UV-Vis. Four novel crystal structures were isolated from reactions of tetraphenylphosphonium salt with zinc(II), cadmium(II), cobalt(II) and copper(II) chloride, each of them producing a unique geometry. Reacting TPPB with ZnCl2, (C24H20P)[ZnCl3(C3H7NO)] results in one (C24H20P+) cation and one [ZnCl3(DMF)] anion (DMF is dimethylformamide). In the anion, the zinc atom is tetrahedrally coordinated by a DMF ligand via the O atom and by three terminal Cl atoms. However, a different structure forms using TPPB with CdCl2, in which the CdX4 ion has a mixture of Cl and Br in a disordered state. As a result of the larger TPP cation, the TPP cation was found to break the -Cu-Cu-Cu-Cu- infinite chain and form dimers in which the smaller Cl atoms are bridging in the middle and the Br atoms are occupying the outer position. Photoluminescence investigation for (C24H20P)2Pb3(Cl/Br)8, zinc and cadmium components reveals a strong emission in the green region at 310 and 350 nm excitation wavelengths, respectively.

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