Regulating the Phase Stability and Bandgap of Quasi-2D Dion–Jacobson Cubic CsSnI3 Perovskite via Intercalating Organic Cations

Currently, as a promising alternative of lead halide perovskites, the nontoxicity lead-free CsSnI3 perovskites have drawn increasing attention. However, the development of tin-based perovskites is still greatly hindered by their...

New Low-Dimensional Hybrid Perovskitoids Based on Lead Bromide with Organic Cations from Charge-Transfer Complexes

We have obtained a series of low-dimensional hybrid perovskitoids (often referred to as perovskites) based on lead bromide. As organic cations, the derivatives of polyaromatic and conjugated molecules, such as anthracene, pyrene and (E)-stilbene, were chosen to form charge-transfer complexes with various organic acceptors for use as highly tunable components of hybrid perovskite solar cells. X-ray diffraction analysis showed these crystalline materials to be new 1D- and pseudo-layered 0D-perovskitoids with lead bromide octahedra featuring different sharing modes, such as in unusual mini-rods of four face- and edge-shared octahedra. Thanks to the low dimensionality, they can be of use in another type of optoelectronic device, photodetectors.

Exploring the structures, stability, and light absorption properties of three thiostannates synthesised at similar conditions

We present the synthesis, crystal structures and optical properties of three thiostannates prepared by using 1-(2-aminoethyl)piperazine (AEPz) as structure directing agent. Two of the thiostannates are layered materials (AEPz-SnS-1 and AEPz:EtOH-SnS-1) consisting of [Sn3S72−]n sheets with organic cations located in-between. The third compound is a molecular thiostannate (Sn2S6(AEPzH2)2) composed of dimeric Sn2S64− and AEPzH22+. In preparation of the layered compounds, the use of AEPz as the only solvent results in AEPz-SnS-1 with regular hexagonal pores and crystallographically disordered organic cations. In contrast, a mixture of AEPz and absolute ethanol gives AEPz:EtOH-SnS-1 with distorted hexagonal pores and ordered cations between the layers. The influence of cation order on the light absorption properties and the material thermal stability was investigated through thermal treatment of the layered compounds up to 200 °C. Both compounds show colour changes when heated, but cation order results in larger thermal stability. For AEPz-SnS-1, a decreased inter-layer distance and substantial loss of organic matter was observed when heated. However, pair distribution function analysis reveals that the local in-layer thiostannate structure of AEPz-SnS-1 remains unchanged. In contrast, AEPz:EtOH-SnS-1 does not undergo noticeable structural changes by the thermal treatment. All materials are optical semiconductors with band gaps of 3.0–3.1 eV.

Band splitting and plurality of excitons in Ruddlesden-Popper metal halides

The organic-inorganic interactions within the hybrid lattice of two-dimensional Ruddlesden-Popper metal halides(RPMH) have consequences on the structural and electronic properties of the material. Such interactions have been primarily investigated through a library of organic cations, keeping the inorganic lead halide lattice component intact. Here, we demonstrate that the role of the organic-inorganic interactions in electronic processes can also be effectively manipulated by the metal cation, particularly moving from heavier lead to lighter tin. We perform in-depth spectroscopic and theoretical analysis of prototypical tin-based RPMH, in which we identify the presence multiple resonances in the optical spectra, which correspond to distinct exciton series. We show that the higher energy excitonic series are composed of electronic transitions from a lower lying valence band which originates from variations in the coordination geometries of the metal halide octahedra induced by subtle changes in the organic-inorganic interactions. Our studies indicate that the deformation induced splitting of the carrier bands is ubiquitous to the Ruddlesden-Popper architectures, although the splitting energies are substantially higher in the tin based systems.

Role of organic cation orientation in formamidine based perovskite materials

The rotation of organic cations is considered to be an important reason for the dynamic changes in stability and photoelectric properties of organic perovskites. However, the specific effect of organic cations rotation on formamidine based perovskite is still unknown. In our work, first-principles calculations based on density functional theory are used to examine the effect of the rotation of formamidine cations in FAPbI3 and FA0.875Cs0.125PbI3. We have comprehensively calculated the structure, electronic and optical properties of them. We found a coupling effect between formamidine cations rotation and cesium atom. This coupling effect changes the inclination angle of octahedron to regulate electron distribution, band gaps, and optical absorption. Hence, changing the cation orientation and substitution atom is a feasible way to dynamically adjust the energy band, dielectric constant and absorption edge of perovskite. Preparing perovskite with tunable properties is just around the corner through this way.

Understanding distortions of inorganic substructures in chloridobismuthates(III)

The molar ratio variations of organic and inorganic reactants of chloridobismuthates(III) with N,N-dimethylethane-1,2-diammonium, [(CH3)2NH(CH2)2NH3]2+, and N,N,N′,N′-tetramethylguanidinium, [NH2C{N(CH3)2}2]+, cations lead to the formation of four different products, namely, tris(N,N-dimethylethane-1,2-diammonium) bis[hexachloridobismuthate(III)], [(CH3)2NH(CH2)2NH3]3[BiCl6]2 (1), catena-poly[N,N-dimethylethane-1,2-diammonium [[tetrachloridobismuthate(III)]-μ-chlorido]], {[(CH3)2NH(CH2)2NH3][BiCl5]} n (2), tris(N,N,N′,N′-tetramethylguanidinium) tri-μ-chlorido-bis[trichloridobismuthate(III)], [NH2C{N(CH3)2}2]3[Bi2Cl9] (3), and catena-poly[N,N,N′,N′-tetramethylguanidinium [[dichloridobismuthate(III)]-di-μ-chlorido]], {[NH2C{N(CH3)2}2][BiCl4]} n (4). The hybrid crystals 1–4, containing relatively large but different organic cations, are composed of four distinct anionic substructures. They are built up from isolated [BiCl6]3− octahedra in 1, from face-sharing bioctahedral [Bi2Cl9]3− units in 3, from polymeric corner-sharing {[BiCl5]2−} n chains in 2 and from edge-sharing {[BiCl4]−} n chains in 4. The distortions shown by the single [BiCl6]3− polyhedra in 1–4 are associated with intrinsic interactions within the anionic substructures and the organic...inorganic substructures interactions, namely, N/C—H...Cl hydrogen bonds. The first factor is the stronger, which is evident in comparison of the experimentally determined geometrical and calculated distortion parameters for the isolated octahedron in 1 to the more complex inorganic substructures in 2–4. The formation of N—H...Cl hydrogen bonds, in terms of their number and strength, is favoured for 1 and 3 containing relatively easily accessed hydrogen-bond acceptors of isolated [BiCl6]3− and [Bi2Cl9]3− units. The studies of the deviations from regularity of the [BiCl6]3− octahedra within inorganic substructures were supported by a survey of the Cambridge Structural Database, which confirmed the role played by different factors in the variations in geometry of the inorganic anions.

Properties of Transport Mediated by the Human Organic Cation Transporter 2 Studied in a Polarized Three-Dimensional Epithelial Cell Culture Model

The renal secretory clearance for organic cations (neurotransmitters, metabolism products and drugs) is mediated by transporters specifically expressed in the basolateral and apical plasma membrane domains of proximal tubule cells. Here, human organic cation transporter 2 (hOCT2) is the main transporter for organic cations in the basolateral membrane domain. In this study, we stably expressed hOCT2 in Madin-Darby Canine Kidney (MDCK) cells and cultivated these cells in the presence of an extracellular matrix to obtain three-dimensional (3D) structures (cysts). The transport properties of hOCT2 expressed in MDCK cysts were compared with those measured using human embryonic kidney cells (HEK293) stably transfected with hOCT2 (hOCT2-HEK cells). In the MDCK cysts, hOCT2 was expressed in the basolateral membrane domain and showed a significant uptake of the fluorescent organic cation 4-(4-(dimethylamino)styryl)-N-methylpyridinium (ASP+) with an affinity (Km) of 3.6 ± 1.2 µM, similar to what was measured in the hOCT2-HEK cells (Km = 3.1 ± 0.2 µM). ASP+ uptake was inhibited by tetraethylammonium (TEA+), tetrapentylammonium (TPA+), metformin and baricitinib both in the hOCT2-HEK cells and the hOCT2- MDCK cysts, even though the apparent affinities of TEA+ and baricitinib were dependent on the expression system. Then, hOCT2 was subjected to the same rapid regulation by inhibition of p56lck tyrosine kinase or calmodulin in the hOCT2-HEK cells and hOCT2- MDCK cysts. However, inhibition of casein kinase II regulated only activity of hOCT2 expressed in MDCK cysts and not in HEK cells. Taken together, these results suggest that the 3D cell culture model is a suitable tool for the functional analysis of hOCT2 transport properties, depending on cell polarization.