Magnetism in 1D and 2D Hybrid Perovskite Induced Through Water-Assisted Self-Assembly Method

Methylammonium lead iodide (MAPbI₃) is an important light-harvesting semiconducting material with excellent optical and electronic properties for the use in optoelectronic devices, including photovoltaic and light-emitting devices. Doping of halide perovskites allows the manipulation of the magnetic, optic, and electronic properties. The successful insertion of magnetic dopants is important to the development of functional devices and is also able to open new potential applications such as in magnetic/semiconducting devices. Therefore, effective strategies to incorporate different ions into the structure have been very appealing. In this work, doped magnetic/semiconducting perovskite microwires have been successfully produced by using a novel strategy involving a self-assembly growth process of [PbI₆]^4- octahedra chains in the presence of liquid water. In this process, a monohydrate compound with a monoclinic structure is formed. The 1D [PbI₆]^4-octahedra chains are stabilized by the presence of both water and MA⁺, forming large channels between chains. This monohydrate compound can easily be reversed to MAPbI₃ through heat treatment or in an evacuated atmosphere eliminating the water present in the channels of the structure. Therefore, we were able to produce paramagnetic perovskite microwires by incorporating iron and manganese ions in the organic channels during the recrystallization process. Afterward, the crystal structure collapses into the 3D perovskite structure through thermal annealing, trapping the magnetic ions within the perovskite structure. Structural and morphological studies confirm that the magnetic ions were successfully introduced in the perovskite structure. From first principles calculations, we determined that the magnetic ions are localized in the interstitial sites. Electric transport characterizations were also carried out to study the influence of the two different magnetic ions on the crystal lattice and charge carrier dynamics. 2D ribbon-like magnetic perovskites were also produced by adding large organic molecules along with magnetic ions through this self-assembly growth process. The introduction of large ammonium cation as butylammonium leads to a 2D layered structure alternately stacked insulating organic spacer layer and inorganic BX₆ slabs. The general chemical formula is (L)₂(A)_n-1B_nX_3n+1, where L is the monovalent organic spacer, A is a monovalent cation, B is a divalent metal cation, X is a halide anion, and <i>n</i> represents the number of BX₆ layers. Structural analysis indicated that the 2D perovskite with a mix number of <i>n</i> is formed without traces of Fe or Mn binary impurity phases. The hydrophobic organic spacer layer provides a natural protective barrier for the penetration of ions and moisture offering long-term stability in the air atmosphere for the perovskites.