Structural diversity in hybrid organic–inorganic lead iodide materials

Abstract

The structural chemistry of hybrid organic-inorganic lead iodide materials has become of increasing significance for energy applications since the discovery and development of perovskite solar cells based on methylammonium lead iodide. Seven new hybrid lead iodide compounds have been synthesized and structurally characterized using single-crystal X-ray diffraction. The lead iodide units in materials templated with bipyridyl, 1,2-bis(4-pyridyl)ethane, 1,2-di(4-pyridyl)ethylene and imidazole adopt one-dimensional chain structures, while crystallization from solutions containing piperazinium cations generates a salt containing isolated [PbI6](4-) octahedral anions. Templating with 4-chlorobenzylammonium lead iodide adopts the well known two-dimensional layered perovskite structure with vertex shared sheets of composition [PbI4](2-) separated by double layers of organic cations. The relationships between the various structures determined, their compositions, stability and hydrogen bonding between the protonated amine and the iodide ions of the PbI6 octahedra are described.

Non‐Perovskite Hybrid Material, Imidazolium Lead Iodide, with Enhanced Stability

“…Although the stoichiometry obtained was also ABX 3 which is conventionally given to perovskite based structures, ImPI is a non‐perovskite hexagonal structure with a cell volume of 1687.80 Å 3 . The crystal structure of ImPI reported here is in agreement with the previous report on it by Weber et al . The single crystal structure of MAPI (synthesized using the protocol mentioned in the “Experimental Section”) was also determined at room temperature for the sake of comparison, Figure b, CCDC number 1822501.…”

“…in 2015 introduced imidazolium lead iodide (ImPI) as one of the seven potential materials for photovoltaic applications. They reported the synthesis of single crystals and the crystal structure of this material along with only a cursory evaluation of the material . Presented here is a detailed comprehensive study of this material in terms of optimisation of the synthesis of single crystals, crystal structural characterization, preparation of high quality thin films by solution processing leading to high surface coverage, and evaluation of the stability (thermal, temporal and phase) of both the single crystals and thin films and their optoelectronic properties.…”

Appraisement of Crystal Expansion in CH3NH3PbI3 on Doping: Improved Photovoltaic Properties

“…However, addition of ImI up to 15 mol % increases the reflection peak intensity, signifying the increased crystallinity of the perovskite film. Beyond 15 mol %, the corresponding diffraction peak signal decreases significantly with increasing ImI content along with the appearance of a new reflection peak at 11.4°, indicating the formation of pure ImPbI 3 hexagonal phase (Figure a) . Thus 15 mol % loading of ImI in perovskite can be considered as the optimum molar percentage to preserve the tetragonal phase of MAPbI 3 .…”

“…The absorption spectra for higher concentrations and for pure ImPbI 3 is shown in Figure S1a. These absorption spectra correspond to higher amounts of ImI (30–60 %) and represent a clear contribution of both phases, with clearly distinguishable bands at 325 and 390 nm arising from low dimensional ImPbI 3 , as previously reported . The authors suggest that it could be attributed to the appearance of imidazolium either as a free cation or ImPbI 3 .…”

Insight into the Mechanochemical Synthesis and Structural Evolution of Hybrid Organic–Inorganic Guanidinium Lead(II) Iodides

“…The straight corner‐sharing perovskite connection can also lead to more exotic structures like 1D chains, zigzag motifs, or staircase‐forming layers . The octahedra in organic–inorganic lead(II) iodides can also be edge‐ and face‐connected, which offers even more structural variety …”