2D Lead Iodide Perovskite with Mercaptan-Containing Amine and Its Exceptional Water Stability.

Two dimensional (2D) hybrid perovskites have attracted a great deal of interest because of their appropriate photovoltaic efficiency and environmental stability. Although some 2D hybrid perovskites with sulfur-containing amines have been reported, the cation having the mercaptan group has not been well explored yet. In this work, cysteamine (Cya, HS(CH2)2NH2), a mercaptan-containing amine, was introduced into 2D hybrid perovskite. Two 2D lead iodides with different structures, (HCya)2PbI4 (1) and (HCya)7Pb4I15 (2), were isolated as a red low-temperature phase and a yellow high-temperature phase, respectively. X-ray single-crystal structural analysis showed that the red phase 1 is a single layered corner-shared perovskite and that the yellow phase 2 is a corner/edge-shared quasi-2D perovskite. A thermo-induced reversible 1 to 2 phase transition was found in this synthetic system. The configuration of HCya cation greatly influences the crystallization equilibrium, generating different structures of the lead halides. The single-crystal structure of 1 is discussed in comparison with that of (HAE)2PbI4 (AE = HO(CH2)2NH2), an analogue of 1. The different effects of OH and SH groups on the 2D frameworks are studied based on their hydrogen bonding properties. More remarkably, although the two perovskites have similar structures, the (HCya)2PbI4 (1) has an intrinsic water stability that is much more stable than (HAE)2PbI4, which should be attributed to the affinity of the SH group with lead on the surface of the lead halide.

Hybrid Lead Iodide Perovskites with Mixed Cations of Thiourea and Methylamine, From One Dimension to Three Dimensions.

Hybrid halide perovskites featuring as new materials of high-performance solar cells have attracted great research interest. The temperature-dependent dimensional transition of halide perovskites is a crucial handle in the preparation of perovskite films. Only the small cations of methylammonium (MA) or formamidinium (FA) have been involved for most of the dimensional transition materials. In this work, thiourea (tu) is introduced into hybrid halide materials. A new series of 1D ribbonlike hybrid lead iodides with tu and MA cations are reported that were crystallographically characterized as MAn(Htu)n+1PbnI4n+1 (n = 1-4 denoted as 1-4, respectively; in 1, MA is replaced by tu). The width of the perovskite ribbon increases from one PbI6 octahedron to four corner-fused octahedra. Compounds 2 and 3 can be turned into a black 3D perovskite after annealing. This is an unusual mixed MA-tu hybrid halide perovskite system, in which the tu molecule plays an important role in manipulating the dimensions and their photoconductive properties. Scanning electron microscopy of the blackened sample shows that there are a lot of regular vent holes on the smooth crystal surface with sizes of hundreds of nanometers. The tunable structures and porous crystals might be advantageous in the sense of material modulation.

A Series of Tetrathiafulvalene Bismuth Chlorides: Effects of Oxidation States of Cations on Structures and Electric Properties.

Most large organic cations in the low-dimensional hybrid halide perovskites deteriorate the photoelectric conversion efficiency of the cells. Integrating electronically active organic components into hybrid metal halides is an effective method to improve their photoelectric properties. In this work, a series of compounds obtained by hybridizing redox-active tetrakis(methylthio)tetrathiafulvalene (TMT-TTF) with bismuth chloride, formulated as [TMT-TTF]4[Bi6Cl22] (1 and 1'), [TMT-TTF]3[Bi4Cl16] (2), [TMT-TTF]2[Bi3Cl13] (3), [TMT-TTF]2[Bi2Cl10] (4), and {[TMT-TTF][Bi2Cl8]}n (5), were crystallographically characterized. These hybrids exhibit changeable oxidation states of the TTF moiety. The radical cation TTF•+ exists in 1 and 1', while a mixed-valence TTF•+/TTF2+ appears in 2 that has never been documented in any compounds and the dication TTF2+ exists in 3-5 that has never been introduced into hybrid organic-inorganic materials. The different charged states of the TTF cations lead to various degrees of connectivity of metal chloride anions, which exert a significant effect on the cation-anion arrangement and result in different supramolecular interactions between TMT-TTF and between cations and anions. The changeable oxidation states of the TTF moiety and varying degrees of metal chloride connectivity provide a good comparison among these hybridized bismuth chlorides. The order of conductivity is 2 > 1 > 1' > 3 ≈ 4 ≫ 5, which results from the synergistic effect of different oxidation states, the packing of TMT-TTF cations, and back charge transfer from the Bi-Cl anion to the TMT-TTF cation. Notably, the electrical conductivity and carrier mobility can be modulated with the fact that compound 2 has the highest performances in the dark, while in light, these properties of 1 and 1' are in turn higher than that of 2. The order of the photocurrent densities is in accordance with the increase of carrier mobility under irradiation of light. This work is the first systematic study of hybrid metal halides with various oxidation states of TTFs and presents a clear structure-property relationship and offers a fresh view on the design of new perovskite materials at the molecular level.

Perfect Self-Assembling of One-Dimensional Lead Iodides with Tetrahedral Cu4I6S4 Clusters: A High-Symmetry Cubic Packing.

Hybrid perovskites are attractive for their applications in photovoltaic devices. We synthesized a novel 1-D hybrid lead iodide, (tu)2Cu2PbI4, in which 1-D PbI3 chains are tetrahedrally orientated to form a crystal lattice with high-symmetry cubic space group Ia3̅ d (No. 230). Optoelectronic and fluorescence properties are studied.