Structure and optical properties of several organic-inorganic hybrids containing corner-sharing chains of bismuth iodide octahedra

Ferroelectric Organic-Inorganic Hybrid Ammonium Halogenobismuthate(III) for Piezoelectric Energy Harvesting

Halogenobismuthate(III) compounds are of recent interest because of their low toxicity and distinct electrical properties. The utility of these materials as ferroelectrics for piezoelectric energy harvesters is still in its early stages. Herein, we report a hybrid ammonium halogenobismuthate(III) [BPBrDMA]2·[BiBr5], crystallizing in a ferroelectrically active polar noncentrosymmetric Pna21 space group. Its noncentrosymmetric structure was confirmed by the detection of the second harmonic generation response. The ferroelectric P-E hysteresis loop measurements on the thin film sample of [BPBrDMA]2·[BiBr5] gave a saturation polarization (Ps) of 5.72 μC cm-2. The piezoresponse force microscopy analysis confirmed its ferroelectric and piezoelectric nature, showing characteristic domain structures and signature hysteresis and butterfly loops. The piezoelectric energy harvesting attributes of [BPBrDMA]2·[BiBr5] were further probed on its polylactic acid (PLA) composites. The 15 wt % [BPBrDMA]2·[BiBr5]-PLA polymer composite resulted in a high output voltage of 26.2 V and power density of 15.47 μW cm-2. The energy harvested from this device was further utilized for charging a 10 μF capacitor within 3 min.

Enhanced Circular Dichroism and Polarized Emission in an Achiral, Low Band Gap Bismuth Iodide Perovskite Derivative

Lead halide perovskites and related main-group halogenido metalates offer unique semiconductor properties and diverse applications in photovoltaics, solid-state lighting, and photocatalysis. Recent advances in incorporating chiral organic cations have led to the emergence of chiral metal-halide semiconductors with intriguing properties, such as chiroptical activity and chirality-induced spin selectivity, enabling the generation and detection of circularly polarized light and spin-polarized electrons for applications in spintronics and quantum information. However, understanding the structural origin of chiroptical activity remains challenging due to macroscopic factors and experimental limitations. In this work, we present an achiral perovskite derivative [Cu2(pyz)3(MeCN)2][Bi3I11] (CuBiI; pyz = pyrazine; MeCN = acetonitrile), which exhibits remarkable circular dichroism (CD) attributed to the material's noncentrosymmetric nature. CuBiI features a unique structure as a poly-threaded iodido bismuthate, with [Bi3I11]2- chains threaded through a cationic two-dimensional coordination polymer. The material possesses a low, direct optical band gap of 1.70 eV. Notably, single crystals display both linear and circular optical activity with a large anisotropy factor of up to 0.16. Surprisingly, despite the absence of chiral building blocks, CuBiI exhibits a significant degree of circularly polarized photoluminescence, reaching 4.9%. This value is comparable to the results achieved by incorporating chiral organic molecules into perovskites, typically ranging from 3-10% at zero magnetic field. Our findings provide insights into the macroscopic origin of CD and offer design guidelines for the development of materials with high chiroptical activity.

Influence of crystal structure and composition on optical and electronic properties of pyridinium-based bismuth iodide complexes

This study investigates the impacts of structure and composition on the optical and electronic properties of a series of pyridinium-based bismuth iodide complexes. Organic substrates with various functional groups, such as 4-aminopyridine (4-Ampy), 4-methylpyridine (4-Mepy), 4-dimethylaminopyridine (4-Dmapy), and 4-pyridinecarbonitrile (4-CNpy) with different electron-donating and electron-withdrawing groups at the para position of the pyridine ring were employed. Crystallographic analysis reveals various bismuth iodide structures, including 1D chains and discrete 0D motifs. The optical band gap of these materials, identified via diffuse reflectance spectroscopy (DRS) and verified with density functional theory (DFT) calculations, is influenced by the crystal packing and stabilising interactions. Through a comprehensive analysis, including Hirshfeld surface (HS) and void assessment, the study underscores the influence of noncovalent intermolecular interactions on crystal packing. Spectroscopic evaluations provide insights into electronic interactions, elucidating the role of electron donor and acceptor substituents within the lattice. Thermogravimetric differential thermal analysis (TG-DTA) indicates structural stability up to 250 °C. Linear sweep voltammetry (LSV) reveals significant conductivity in the range of 10-20 mS per pixel at 298.15 K. X-ray absorption spectroscopy (XAS) at the Bi L3 edge indicates a similar oxidation state and electronic environment across all samples, underscoring the role of bismuth centres surrounded by iodides.

Meltable Hybrid Antimony and Bismuth Iodide One-Dimensional Perovskites

Hybrid lead-halide perovskites have been studied extensively for their promising optoelectronic properties and prospective applications, including photovoltaics, solid-state lighting, and radiation detection. Research into these materials has also been aided by the simple and low-temperature synthetic conditions involved in solution-state deposition/crystallization or melt-processing techniques. However, concern over lead toxicity has plagued the field since its infancy. One of the most promising routes to mitigating toxicity in hybrid perovskite materials is substituting isoelectronic Bi(III) for Pb(II). Various methods have been developed to allow pnictide-based systems to capture properties of the Pb(II) analogues, but the ability to melt extended hybrid pnictide-halide materials has not been investigated. In this work, we prepare a series of one-dimensional antimony- and bismuth-iodide hybrid materials employing tetramethylpiperazinium (TMPZ)-related cations. We observe, for the first time, the ability to melt extended hybrid pnictide-halide materials for both the Sb(III) and Bi(III) systems. Additionally, we find that Sb(III) analogues melt at lower temperatures and attribute this observation to structural changes induced by the increased stereochemical activity of the Sb(III) lone pair coupled with the reduction in effective dimensionality due to steric interactions with the organic cations. Finally, we demonstrate the ability to melt process phase pure thin films of (S-MeTMPZ)SbI5.

Syntheses, structures, photoelectric properties and photocatalysis of iodobismuthate hybrids with lanthanide complex cations

New iodobismuthate hybrids with lanthanide complex counter cations, [Ln(DMF)₈][Bi₂I₉] (Ln = La (1), Eu (2)) and [Tb(DMF)₈]₂[Bi₂I₉]₂ (3) (DMF = N,N-dimethylformamide), were prepared using solvated Ln(III) complexes formed in situ as structure-directing agents. The dimeric [Bi₂I₉]^3- anion moieties of compounds 1-3 are aggregated by two slightly twisted BiI₆ octahedra through face-sharing mode. The different crystal structures of 1-3 are due to the different I⋯I and C-H⋯I hydrogen bond interactions. Compounds 1-3 have narrow semiconducting band gaps at 2.23, 1.91 and 1.94 eV, respectively. Under Xe light irradiation, they exhibit steady photocurrent densities that are 1.81, 2.10 and 2.18 times higher than that of pure BiI₃, respectively. Compounds 2 and 3 exhibited higher catalytic activities than 1 in the photodegradation of organic dyes CV and RhB, which are attributed to the stronger photocurrent response derived from the redox cycles of Eu³⁺/Eu²⁺ and Tb⁴⁺/Tb³⁺.

Establishing Family Relations in Group 15 Halogenido Metalates with the Largest Molecular Antimony Iodide Anion

Studying structurally related families of compounds is a valuable tool in understanding and predicting material properties and has been extensively used for metal halide perovskites. Due to the variable anion structures in group 15 halogenido metalates, similar family relations are still largely missing. Herein, we present compounds featuring the [Sb_2n I_6n+4 ]^4- family of anions, including the first n=5 member in [Hpyz]₄ [Sb₁₀ I₃₄ ] (Hpyz=pyrazinium), which contains the largest halogenido pentelate anion reported to date. The optical properties of compounds featuring n=1-5 anions show a clear trend as well as an outlier, a low band gap of 1.72 eV for [Hpyz]₄ [Sb₁₀ I₃₄ ], that can be well understood using quantum chemical investigations. Also using SbI₃ and [H₂ NMe₂ ]₃ [SbI₆ ], a compound featuring a single octahedral [SbI₆ ]^3- unit, as limiting cases, we show that structure-property relationships can be established in group 15 halogenido metalates in a similar way as in metal halide perovskites, thus providing a framework for understanding new and known compounds in this emerging class of materials.

A new metal complex-templated silver iodobismuthate exhibiting photocurrent response and photocatalytic property

An organic-inorganic hybrid silver iodobismuthate characteristic of the infrequent [Ag₂BiI₆L₂] cluster (L = I or I₃) and with a unique Ag/Bi molar ratio (2/1), namely, [Zn(bipy)₃]₂Ag₂BiI₆(I)_1.355(I₃)_1.645 (bipy = 2,2'-bipyridine; 1), was solvothermally synthesized, and structurally, optically, and theoretically studied. Intriguingly, compound 1 exhibited semiconductor behavior with an optical band gap of 2.33 eV, which endowed it with excellent photoelectric and photocatalytic properties. Electronic structure calculations further revealed that the relative separate conduction band (CB) and valence band (VB) in compound 1 may be responsible for the good optical activity. This study also includes the Hirshfeld surface analyses, thermogravimetric measurements and X-ray photoelectron spectroscopy (XPS) characterization.

Expanding Bismuth Trihalide Coordination Chemistry with Trimethyltriazacyclohexane and Trimethyltriazacyclononane

1,3,5-Trimethyltriazacyclohexane, Me₃tach, readily adds to bismuth triiodide to form a variety of new coordination compounds depending on the stoichiometry, solvent, and crystallization conditions. X-ray crystallographic evidence has been obtained for both 2:1 and 1:1 Me₃tach:Bi complexes with formulas of [(Me₃tach)₂BiI₂][(Me₃tach)BiI₄], [(Me₃tach)₂BiI₂]₃[Bi₂I₉][I][HMe₃tach]·THF, and (Me₃tach)BiI₃(py)₂. The related chloride structure (Me₃tach)BiCl₃(py)₂ forms from BiCl₃. The structure of (Me₃tacn)BiI₃ with the larger chelate, 1,4,7-trimethyltriazacyclononane, Me₃tacn, was obtained for comparison, and the polymeric structure of BiI₃ in THF was defined as [BiI(THF)(μ-I)₂]_n.

Recent advances on structural, thermal, vibrational, optical, phase transitions, and catalysis properties of alkylenediammonium halogenometallate materials (Metal: Bi, Sb, Halogen: Cl, Br, I)

This paper aims to review recent advances on synthesis, crystal structures, thermal, spectroscopic, phase transitions, optical, dielectric, and catalysis properties of hydrate and anhydrous alkylenediammonium halogenometallates materials (Metal: Bi, Sb, Halogen: Cl, Br, I). These hybrid materials present rich structural diversities based on octahedra forming infinite zero dimensional, 1-dimensional chains, 2-dimensional layers, discrete bioctahedra, and discrete tetramer units. The effect, contribution and importance of hydrogen bonding N–H … X (X: Cl, Br, I) are reviewed in terms of solid state relationship. Particularly, a comparative study is made on hydrate and anyhdrous aliphatic chlorobismuthates with alkylenediammonium +NH3(CH2) n NH3 + based on structural data and V/Z variation with (CH2) n chains (n = 2–8, 12), and variation of BiCl6 3− Raman frequencies modes versus (CH2) n chains (n = 3–8). Hydrate salts with (n = 3, 12) consist of isolated BiCl6 3− anions and two water molecules, against others ones with isolated anionic chains [BiCl5 2−] n or Bi2Cl10 4− dimers, formed by distorted octahedra BiCl6 3− sharing corners, vices or edges. The reviewed optical and electronic band gaps suggested interesting compounds with band gaps (1.85–2.4 eV), as suitable materials in optoelectronic properties, photoactive layer in solution-processed photovoltaics, and bio-imaging or photovoltaic applications. It was concluded that iodobismuthate salts have generally the lowest bands gap, compared to that of bromo and chlorobismuthate slats. Catalysis proprieties are reviewed n fast (RhB) degradation under dark conditions for (C4N2H7)4Bi2Cl10, (C5H9N2)BiI4, and {(H-BPA)4·[(BiI6)I13]·2I3} n , and in organic salts synthesis under solvent-free conditions. Herein NH3(CH2) n NH3BiCl5 (n = 5–7) salts were used as highly efficient catalysts, which is a novel tendency in chlorobismuthate researchs in the green chemistry field.

An Experimental and Theoretical Study of the Optical Properties of (C2H7N4O)2BiCl5 for an Optoelectronic Application

This study explores the electronic properties of (C2H7N4O)2BiCl5 using the density functional theory (DFT) method, which was compared with the experimental data. The band structure of the compound indicated that it is a direct semiconductor with a band gap energy of 3.54 eV, which was comparable with the value (3.20 eV) obtained experimentally from the UV–vis spectroscopy. The density of state study showed that the conduction band was formed mainly by Bi 6p, C 2p, and N 2p states, while the valence band was formed mainly by Cl 2p, O 2p, and N 2p states. Hirshfeld surface analysis and enrichment ratio (E) were further used to investigate and quantify the intermolecular interactions within the compound. These studies established that the most important role in the stability of the structure of this crystalline material was provided by hydrogen bonding and π–π stacking interactions. The crystalline morphology of the compound was determined using BFDH simulation, based on the single-crystal structure result. Furthermore, Fourier transform infrared spectroscopy (FTIR) was used to study the vibrational modes of carbamoyl-ganidinium cations. The charge transfer process within the anionic chains of [BiCl5]∝, studied using photoluminescence spectroscopy, resulted in a broad emission band with two positions of maxima centered at 336 and 358 nm. This work offers a good understanding of the optical, structural, as well as the electrical properties of (C2H7N4O)2BiCl5, which are necessary in its applications in areas such as multifunctional magnetic, optoelectronic, and photonic systems.

Ultrafast Solution-Phase Photophysical and Photochemical Dynamics of Hexaiodobismuthate(III), the Heart of Bismuth Halide Perovskite Solar Cells

The ultrafast relaxation pathways in a hexaiodide bismuth(III) complex, BiI₆^3-, excited at 530 nm in acetonitrile solution are studied by means of femtosecond transient absorption spectroscopy supported by steady-state absorption/emission measurements and DFT computations. Radiationless relaxation out of the Franck-Condon, largely metal-centered (MC) triply degenerate ³T_1u state (46 ± 19 fs), is driven by vibronic coupling due to the Jahn-Teller effect in the excited state. The relaxation populates two lower-energy states: a ligand-to-metal charge transfer (LMCT) excited state of ³π I(5p_π) → Bi(6p) nature and a luminescent "trap" ³A_1u(³P₀) MC state. Coherent population transfer from the initial ³T_1u into the ³π LMCT state occurs in an oscillatory, stepwise manner at ∼190 and ∼550 fs with a population ratio of ∼4:1. The ³π LMCT state decays with a 2.9 ps lifetime, yielding two short-lived reaction intermediates of which the first one reforms the parent ground state with a 15 ps time constant, and the second one decays on a ∼5 ps timescale generating the triplet product species, which persists to the longest 2 ns delay times investigated. This product is identified as the η² metal-ligated diiodide-bismuth adduct with the intramolecularly formed I-I bond, [(η²-I₂)Bi(II)I₄]^3-, which is the species of interest for solar energy conversion and storage applications. The lifetime of the "trap" ³A_1u state is estimated to be 13 ns from the photoluminescence quenching of BiI₆^3-. The findings give insight into the excited-state relaxation dynamics and the photochemical reaction mechanisms in halide complexes of heavy ns² metal ions.

From Zero- to One-Dimensional, Opportunities and Caveats of Hybrid Iodobismuthates for Optoelectronic Applications

The association of the electron acceptor 4,4'-amino-bipyridinium (AmV²⁺) dication and BiI₃ in an acidic solution affords three organic-inorganic hybrid materials, (AmV)₃(BiI₆)₂ (1), (AmV)₂(Bi₄I₁₆) (2), and (AmV)BiI₅ (3), whose structures are based on isolated BiI₆^3- and Bi₄I₁₆^4- anion clusters in 1 and 2, respectively, and on a one-dimensional (1D) chain of trans-connected corner-sharing octahedra in 3. In contrast with known methylviologen-based hybrids, these compounds are more soluble in polar solvents, allowing thin film formation by spin-coating. (AmV)BiI₅ exhibits a broad absorption band in the visible region leading to an optical bandgap of 1.54 eV and shows a PV effect as demonstrated by a significant open-circuit voltage close to 500 mV. The electronic structure of the three compounds has been investigated using first-principles calculations based on density functional theory (DFT). Unexpectedly, despite the trans-connected corner-shared octahedra, for (AmV)BiI₅, the valence state shows no coupling along the wire direction, leading to a high effective mass for holes, while in contrast, the strong coupling between Bi 6p_x orbitals in the same direction at the conduction band minimum suggests excellent electron transport properties. This contributes to the low current output leading to the low efficiency of perovskite solar cells based on (AmV)BiI₅. Further insight is provided for trans- and cis-MI₅ 1D model structures (M = Bi or Pb) based on DFT investigations.

Strong Second- and Third-Harmonic Generation in 1D Chiral Hybrid Bismuth Halides

Breaking the symmetry of a crystal structure can enable even-order nonlinear activities, including second-harmonic generation (SHG). The emerging chiral hybrid organic-inorganic metal halides feature unique optical and electronic properties and flexible crystal structures, making them a class of promising nonlinear optical materials. However, their nonlinear response performances are currently inferior to traditional nonlinear crystals, because of the lack of research on resonant enhancement and third-harmonic generation (THG). Herein, we designed chiral hybrid bismuth halides with naturally nonsymmetrical structure to enable SHG. Simultaneously, these chiral compounds preserve 1D crystal structures to create strong free exciton, broad self-trapped exciton (STE), and discrete band energy levels, which facilitate the resonant enhancement of SHG and THG susceptibilities. These new chiral films showcase superior effective SHG susceptibility (χ⁽²⁾ ∼ 130.5 pm V^-1 at an interesting wavelength of 1550 nm), exceeding that of the reference, a commercial LiNbO₃ (χ⁽²⁾ ∼ 83.4 pm V^-1) single-crystal film. Furthermore, their THG intensities are even higher than their SHG intensities, with effective THG susceptibility (χ⁽³⁾) being ∼9.0 × 10⁶ pm² V^-2 at 1550 nm (37 times that of the reference monolayer WS₂). Their high SHG and THG performances indicate the promising future of these 1D chiral hybrid bismuth halides toward nonlinear optical applications.

Multiple Roles of 1,4-Diazabicyclo[2.2.2]octane in the Solvothermal Synthesis of Iodobismuthates

Hybrid bismuth-containing halides are emerging as alternative candidates to lead-containing perovskites for light-harvesting applications, as Bi3+ is isoelectronic with Pb2+ and the presence of an active lone pair of electrons is expected to result in outstanding charge-carrier transport properties. Here, we report a family of one binary and three ternary iodobismuthates containing 1,4-diazabicyclo[2.2.2]octane (DABCO). These materials have been prepared solvothermally and their crystal structures, thermal stability, and optical properties determined. Reactions carried out in the presence of bismuth iodide and DABCO produced (C6H12N2)BiI3 (1), which consists of hybrid ribbons in which pairs of edge-sharing bismuth octahedra are linked by DABCO ligands. Short I···I contacts give rise to a three-dimensional network. Similar reactions in the presence of copper iodide produced (C8H17N2)2Bi2Cu2I10 (2) and [(C6H13N2)2BiCu2I7](C2H5OH) (3) in which either ethylated DABCO cations (EtDABCO)+ or monoprotonated DABCO cations (DABCOH)+ are coordinated to copper in discrete tetranuclear and trinuclear clusters, respectively. In the presence of potassium iodide, a unique three-dimensional framework, (C6H14N2)[(C6H12N2)KBiI6] (4), was formed, which contains one-dimensional hexagonal channels approximately 6 Å in diameter. The optical band gaps of these materials, which are semiconductors, range between 1.82 and 2.27 eV, with the lowest values found for the copper-containing discrete clusters. Preliminary results on the preparation of thin films are presented.

Large-Grained All-Inorganic Bismuth-Based Perovskites with Narrow Band Gap via Lewis Acid-Base Adduct Approach

Bismuth halide perovskites have recently been considered a potential alternative to lead halide analogues due to their low toxicity and high stability. However, the layered flake structure and wide band gap limit their applications in perovskite solar cells (PSCs). We herein show that large-grained all-inorganic bismuth-based perovskites with a narrow band gap can be obtained from a Lewis acid-base adduct reaction under ambient conditions. Thiourea (CH₄N₂S) is utilized as a Lewis base to interact with BiI₃, confirmed with infrared (IR) spectra. The strong coordination between thiourea and the Bi³⁺ center could slow down the perovskite crystallization and promote the preferred orientation of the perovskite crystals with a hexagonal phase. The morphology of the perovskite films varies dramatically with an increase of molar ratio of BiI₃ and thiourea in the precursor. The perovskites derived from a BiI₃/thiourea ratio of 1:2 display extrathick grains, higher surface coverage, extended light absorption, higher crystallinity, and similar air stability compared to the pristine sample. The power conversion efficiency (PCE) of the thiourea-induced bismuth perovskite solar cells is significantly enhanced due to the higher surface coverage and the broader absorption of the perovskite film.

A Potential Checkmate to Lead: Bismuth in Organometal Halide Perovskites, Structure, Properties, and Applications

The remarkable optoelectronic properties and considerable performance of the organo lead-halide perovskites (PVKs) in various optoelectronic applications grasp tremendous scientific attention. However, the existence of the toxic lead in these compounds is threatening human health and remains a major concern in the way of their commercialization. To address this issue, numerous nontoxic alternatives have been reported. Among these alternatives, bismuth-based PVKs have emerged as a promising substitute because of similar optoelectronic properties and extended environmental stability. This work communicates briefly about the possible lead-alternatives and explores bismuth-based perovskites comprehensively, in terms of their structures, optoelectronic properties, and applications. A brief description of lead-toxification is provided and the possible Pb-alternatives from the periodic table are scrutinized. Then, the classification and crystal structures of various Bi-based perovskites are elaborated on. Detailed optoelectronic properties of Bi-based perovskites are also described and their optoelectronic applications are abridged. The overall photovoltaic applications along with device characteristics (i.e., V OC, J SC, fill factor, FF, and power conversion efficiency, PCE), fabrication method, device architecture, and operational stability are also summarized. Finally, a conclusion is drawn where a brief outlook highlights the challenges that hamper the future progress of Bi-based optoelectronic devices and suggestions for future directions are provided.

Non-transient thermo-/photochromism of iodobismuthate hybrids directed by solvated metal cations

Two iodobismuthate-based organic-inorganic hybrids, [M(DMSO)₈][Bi₂I₉] (M = La (1), Bi (2)), have been successfully designed and synthesized by using solvated metal cations as structure-directing agents (SDAs). 1 displays transient high-temperature thermochromism, which is similar to that of the characteristic low-temperature thermochromic properties of bulk bismuth iodide and iodobismuthate hybrids. In contrast, 2 exhibits distinguishing non-transient thermochromic properties stimulated by the different temperature ranges of the thermal treatments. More importantly, a comparison of the optical inertness of 1 and 2 also reveals novel photochromic behavior. The completely different thermo-/photo-responsive properties of 1 and 2 are mainly ascribed to the different binding abilities of the central metal cations with DMSO molecules, which cause a distinct transformation of the inorganic moiety and consequent modulation of band gaps.

Organic molecule stabilized bismuth iodide nanoparticles: a hybrid system with multifunctional physical properties

An organic-inorganic hybrid system of aniline stabilized bismuth iodide nanoparticles (ABI) was synthesized and investigated for its dielectric properties, AC-conductivity, polarization hysteresis and non-volatile memory performances. The X-ray diffraction result indicates the single phase crystalline nature of the nanoparticles and a microscopic image shows the homogeneous distribution of the bismuth iodide nanoparticles within the organic matrix. The material has exhibited a moderate dielectric performance via an interfacial polarization mechanism. The decrease in dielectric constant with frequency is correlated with the carrier concentration and diffusion potential, and the behaviour revealed that the halide ion mediated polaron migration controls the overall relaxation and conductivity properties of the material. Octahedral distortion of bismuth iodide, through halide ion migration, induced a hysteresis loop in polarization-electric field (P-E) characteristics. The device fabricated with the aniline stabilized bismuth iodide nanoparticles exhibited a space-charge limited current and trap assisted tunneling mechanism for the charge transport process. The non-volatile property reveals that the device has the ability to store binary information and has potential for memory applications.

(HPy)2(Py)CuBi3I12, a low bandgap metal halide photoconductor

Bismuth halides represent an emergent class of materials that combines semiconductor properties with non-toxic constituents. However, many simple bismuth halide compounds feature bandgaps that are significantly higher than those of the lead halide perovskites, which they are supposed to replace. One way to address this issue is the preparation of multinary metal halide materials that feature an additional metal ion. Here, we report on the synthesis and properties of (HPy)2(Py)CuBi3I12 (1) a new copper iodido bismuthate, a photoconductor, which shows a low band gap of 1.59 eV and good thermal and air stability.

Crystal and Band-Gap Engineering of One-Dimensional Antimony/Bismuth-Based Organic-Inorganic Hybrids

Hybrid halide perovskites are emerging semiconducting materials with a diverse set of remarkable optoelectronic properties. Besides the widely studied lead halide perovskites, Pb-free metal halides such as Bi- and Sb-containing hybrid organic-inorganic materials have shown potential as semiconductors and have been deemed candidates for optoelectronic devices. Here, we report a series of 1D Sb/Bi-based organic-inorganic hybrid alloys: [4ApyH]Sb_xBi_1-xI_yBr_4-y, where 4ApyH stands for the 4-aminopyridine cations. These compounds are assembled by edge-sharing octahedral [MX₆] units stabilizing 1D chains with organic cations filled in between. The crystallographic data of eight selected complexes show that [4ApyH]Sb_xBi_1-xI_yBr_4-y has at least five phases (space group) with the difference metal and halogen content: Pbca ([4ApyH]BiI₄), Pca2₁ ([4ApyH]Sb_0.5Bi_0.5I₄), P2₁/c ([4ApyH]SbI₄ (100 K), [4ApyH]BiI₂Br₂, [4ApyH]BiBr₄, and [4ApyH]SbBr₄ (100 K)), I2/a ([4ApyH]Sb_0.5Bi_0.5I₂Br₂and [4ApyH]SbI₂Br₂), and C2/c ([4ApyH]SbI₄ (298 K) and [4ApyH]SbBr₄ (298 K)). Powder X-ray diffraction shows that the phase of the sample changes with a change of the metal and halogen ratios, and the change law accords with Vegard's law. The optical band gaps are heavily affected by the metal and halide contents, ranging from 1.94 eV for [4ApyH]BiI₄ to 2.73 eV for [4ApyH]SbBr₄. When Sb substitutes for Bi to form an alloy, the band gap increases from 1.94 for [4ApyH]BiI₄ to 1.67 eV for [4ApyH]SbI₄, from 2.13 eV for [4ApyH]BiI₂Br₂ to 2.41 eV for [4ApyH]SbI₂Br₂, and from 2.55 eV for [4ApyH]BiBr₄ to 2.73 eV for [4ApyH]SbBr₄. The conductivity of [4ApyH]Sb_xBi_1-xI₄ increased from ∼1.00 × 10^-15 to 2.14 × 10^-8 S cm^-1 with an increase of the Sb content. Solution-deposited thin films of the nine complexes show the same (110) orientation, displaying a parallel growth orientation with respect to the substrate. The devices of [4ApyH]Sb_0.8Bi_0.2I₄ and [4ApyH]SbI₄ demonstrated stable open-circuit photovoltages of 0.55 and 0.44 V, steady-state short-circuit photocurrent densities of 1.52 and 1.81 mA cm^-2, and light-to-electrical energy conversion efficiencies of 0.29% and 0.30%, respectively.

Tracking the dimensional conversion process of semiconducting lead bromide perovskites by mass spectroscopy, powder X-ray diffraction, microcalorimetry and crystallography

The structural information of a material in both the solid state and solution state is essential to the in-depth understanding of the properties of inorganic-organic hybrid materials. A one-dimensional (1D) lead bromide formulated as [H][NH₃(CH₂)₂SS(CH₂)₂NH₃][H₂O][PbBr₅] (1) could be converted into a new two-dimensional (2D) complex, [NH₃(CH₂)₂SS(CH₂)₂NH₃][PbBr₄] (2), by soaking the crystals in water. The isolated 2D compound showed single-layer lead-halide perovskite structures. Electrospray ionization mass spectrometry (ESI-MS) analyses of the reaction solution revealed that the [PbBr₃]^- fragments are initially formed from the rapid decomposition of the 1D [PbBr₅]^3- chains and subsequently reassemble into 2D [PbBr₄]^2- layers, which was verified by powder X-ray diffraction (PXRD) and microcalorimetry. Because of the decomposition and reassembly process, complex 1 could be used as a precursor to synthesize M²⁺-doped 2D lead bromide perovskites, namely, Mn@2, Ni@2 and Cd@2. In addition, preliminary tests indicated that complex 2 exhibited a lower optical band gap (3.25 eV) and higher electrical conductivity (3.2 × 10^-11 S cm^-1) than complex 1 (3.38 eV, 5.4 × 10^-12 S cm^-1).

Low-dimensional bismuth(III) iodide hybrid material with high activity for the fast removal of rhodamine B

Organic-inorganic hybrid lead-based perovskite crystal materials have been widely studied due to their excellent optical-electronic properties. However, the toxicity of lead limits their widespread use. Here, a lead-free perovskite-type compound, tetrakis(1,2,3-trimethylimidazolium) di-μ₃-iodido-tetra-μ₂-iodido-decaiodidotetrabismuth(III), (C₆H₁₁N₂)₄[Bi₄I₁₆], has been successfully synthesized by a simple solvothermal method. It exhibits a zero-dimensional (0D) tetrameric structure, including edge-sharing [Bi₄I₁₆]^4- distorted octahedra. The band gap of 2.0 eV is close to that of (NH₄)₃[Bi₂I₉]. Degradation ability measurements were performed to examine the potential application of this material as an alternative for waste-water treatment.

Lead-Free Hybrid Perovskite Absorbers for Viable Application: Can We Eat the Cake and Have It too?

Many years since the booming of research on perovskite solar cells (PSCs), the hybrid perovskite materials developed for photovoltaic application form three main categories since 2009: (i) high-performance unstable lead-containing perovskites, (ii) low-performance lead-free perovskites, and (iii) moderate performance and stable lead-containing perovskites. The search for alternative materials to replace lead leads to the second group of perovskite materials. To date, a number of these compounds have been synthesized and applied in photovoltaic devices. Here, lead-free hybrid light absorbers used in PV devices are focused and their recent developments in related solar cell applications are reviewed comprehensively. In the first part, group 14 metals (Sn and Ge)-based perovskites are introduced with more emphasis on the optimization of Sn-based PSCs. Then concerns on halide hybrids of group 15 metals (Bi and Sb) are raised, which are mainly perovskite derivatives. At the same time, transition metal Cu-based perovskites are also referred. In the end, an outlook is given on the design strategy of lead-free halide hybrid absorbers for photovoltaic applications. It is believed that this timely review can represent our unique view of the field and shed some light on the direction of development of such promising materials.

Iodoargentate/iodobismuthate-based materials hybridized with lanthanide-containing metalloviologens: thermochromic behaviors and photocurrent responses

New hybrids combined metalloviologens with Ag/Cu iodides exhibit reversible thermochromisms, photocurrent responses, whose mechanisms are disclosed.

Synthesis, structure and optoelectronic properties of hybrid iodobismuthate & iodoantimonate semiconducting materials

The syntheses, structures and optical absorption spectra of five iodobismuthate and nine iodoantimonate hybrid materials are presented.