Zeyu Deng

The synthesis, structure and electronic properties of a lead-free hybrid inorganic–organic double perovskite (MA)2KBiCl6 (MA = methylammonium)

In a search for lead-free materials that could be used as alternatives to the hybrid perovskites, (MA)PbX3, in photovoltaic applications, we have discovered a hybrid double perovskite, (MA)2KBiCl6, which shows strong similarities to the lead analogues. Spectroscopic measurements and nanoindentation studies are combined with density functional calculations to reveal the properties of this interesting system.

Exploring the properties of lead-free hybrid double perovskites using a combined computational-experimental approach

Density functional theory screening of the hybrid double perovskites (MA)2BIBiX6 (BI = K, Cu, Ag, Tl; X = Cl, Br, I) shows that systems with band gaps similar to those of the MAPbX3 lead compounds can be expected for BI = Cu, Ag, Tl. Motivated by these findings, (MA)2TlBiBr6, isoelectronic with MAPbBr3, was synthesised and found to have a band gap of ∼2.0 eV.

Synthesis and Characterization of the Rare-Earth Hybrid Double Perovskites: (CH3NH3)2KGdCl6 and (CH3NH3)2KYCl6

Two hybrid rare-earth double perovskites, (CH3NH3)2KGdCl6 and (CH3NH3)2KYCl6, have been synthesized by a solution evaporation method and their structures determined by variable temperature single-crystal X-ray diffraction. The diffraction results show that at room temperature both perovskites adopt a rhombohedral structure with R3̅m symmetry, as found previously for (MA)2KBiCl6, and lattice parameters of a = 7.7704(5) Å and c = 20.945(2) Å for (MA)2KGdCl6 and a = 7.6212(12) Å and c = 20.742(4) Å for (MA)2KYCl6. Both phases exhibit a rhombohedral-to-cubic phase transition on heating to ∼435 K for (MA)2KYCl6 and ∼375 K for (MA)2KGdCl6. Density functional calculations on the rhombohedral phase indicate that both materials have large direct band gaps, are mechanically stable, and, in the case of (MA)2KGdCl6, could exhibit magnetic ordering at low temperatures.

Computational Data for "The Synthesis and Characterization of the Rare-Earth Hybrid Double Perovskites: (CH₃NH₃)₂KGdCl₆ and (CH₃NH₃)₂KYCl₆"

This repository contains the data from the computational work done in the paper. The data provide enough information to reproduce the results shown in the paper.

The Competition Between Mechanical Stability and Charge Carrier Mobility in MA-based Hybrid Perovskites: Insight from DFT

Hybrid organic–inorganic perovskites and their inorganic analogues, such as MAPbI3 (MA = methylammonium, CH3NH3) and CsPbI3, are currently under intense investigation due to their high-power conversion efficiencies and low cost for solar cell applications. Herein, we investigate the effect of methylammonium and the inorganic A-cations on the elastic and related transport properties of halide perovskites using van der Waals (vdW) corrected density functional theory (DFT) calculations. For inorganic halide perovskites we find that the bonding within the inorganic framework is mainly responsible for their elastic behavior. However, our DFT calculations show that when a MA cation is substituted into the structure the combined effects of stericity (conformation) and hydrogen-framework interactions improve the materials resistance to deformation. For example, the orientationally-averaged Youngs modulus of orthorhombic MAPbI3 increases by about 19% compared to the equivalent inorganic series of structures. We also find that, within the carrier-acoustic phonon scattering regime, the electron and hole carrier mobilities of hybrid halide perovskites are lowered by the hydrogen-bonding-induced tilting of the inorganic octahedra. Taken together, these results can help guide the optimization of the mechanical and transport properties of perovskite-based solar cell materials.

Octahedral connectivity and its role in determining the phase stabilities and electronic structures of low-dimensional, perovskite-related iodoplumbates

We describe a single crystal X-ray diffraction study and computational analysis of three guanidinium (Gua) based low-dimensional iodoplumbates with one edge-sharing and two corner-sharing octahedral connectivities, respectively. (Gua)3PbI5, which is reported for the first time, has a 1D corner-sharing octahedral chain structure. GuaPbI3 adopts a 1D edge-sharing octahedral chain structure in preference to structures that are either 3D and corner-sharing (i.e., perovskite) or 1D and face-sharing. (Gua)2PbI4 exhibits 2D corner-sharing octahedral connectivity in agreement with previous work. Density functional theory calculations are used to gain insight into the relative stabilities of the three polymorphs of GuaPbI3 and to assess how the connectivity and dimensionality of the octahedral framework influence the electronic structure of each of the hybrid perovskites studied.

Computational Data for "Factors influencing the mechanical properties of formamidinium lead halides and related hybrid perovskites"

This repository contains the data from the computational work done in the paper. The data provide enough information to reproduce the results shown in the paper.