Lead-free Organic Inorganic Hybrid Research Articles

Band-Gap Narrowing and Electric Transport Regulation of Hybrid Perovskites via Pressure Engineering.

Lead-free organic-inorganic hybrid perovskites are one class of promising optoelectronic materials that have attracted much attention due to their outstanding stability and environmentally friendly nature. However, the intrinsic band gap far from the Shockley-Queisser limit and the inferior electrical properties largely limit their applicability. Here, a considerable band-gap narrowing from 2.43 to 1.64 eV with the compression rate up to 32.5% is achieved via high-pressure engineering in the lead-free hybrid perovskite MA3Sb2I9. Meanwhile, the electric transport process changes from the initial interaction of both ions and electrons to only the contribution of electrons upon compression. The alteration in electrical characteristics is ascribed to the vibration limitation of organic ions and the enhanced orbital overlap, resulting from the reduction of the Sb-I bond length through pressure-induced phase transitions. This work not only systematically investigates the correlation between the structural and optoelectronic properties of MA3Sb2I9 but also provides a potential pathway for optimizing electrical properties in lead-free hybrid perovskites.

Reversible structural transformation of metastable lead-free organic–inorganic hybrid bismuth halide single crystals

Lead-free organic–inorganic hybrid bismuth halides have been recognized as promising alternatives to lead-based perovskites for low-toxic and environmentally-friendly optoelectronic applications.

Synthesis, crystal structure, optical properties and bactericidal activity of a new organic-inorganic hybrid: Benzyl triethylaminium tetrachloromanganate(II)

In this work, a lead-free organic-inorganic hybrid crystal with dual functions of green-emission and bactericidal activity, benzyl triethylaminium tetrachloromanganate(II) ([BzTEA]2[MnCl4]), was synthesized by the slow evaporation solution growth technology and characterized by single-crystal and power X-ray diffraction, IR spectrum, Scanning Electron microscopy, and PL spectrum. The compound crystallized in the monoclinic space group P21/c. The thermal study revealed that the material showed good thermal stability and can be used for applications below 222.1 °C. The material had excellent optical properties as it fluoresced green under 350 nm UV light. The compound exhibited favorable bactericidal activity against Staphylococcus aureus and Escherichia coli.

Photophysical Properties of S = 5/2 Zigzag-1D (2-Bromoethylammonium)3MnBr5 Antiferromagnet.

It has been challenging to design multifunctional lead-free organic-inorganic hybrid halides that can exhibit fascinating magnetic and photoluminescence properties since the dimensionality of the compounds has a contrasting impact on them. In this context, our newly synthesized compound (2-bromoethylammonium)3MnBr5 (BEAMBr) crystallizes in the monoclinic C2/c space group with corner-sharing zigzag 1D chains of MnBr6 distorted octahedra. Intriguingly, it exhibits a long-range antiferromagnetic ordering at low temperature (∼2.5 K) along with a typical low-dimensional broad magnetic susceptibility hump. The magnetic properties modeled by the exact diagonalization approach indicate strong intrachain and weak interchain interactions with J1 = -50.1 K, J2 = -13.0 K, and J' = -1.25 K, respectively, suggesting excellent one-dimensionality. In addition, BEAMBr displays orange-red emission with a photoluminescence quantum yield of 15.2%. Interestingly, electron-phonon coupling was observed in this soft distorted compound with coupling strength γLO = 128.3 meV, confirmed from the analysis of temperature-dependent emission line width broadening and Raman spectra.

Synthesis, crystal structure and optical properties of the quasi-0D lead-free organic-inorganic hybrid crystal (C6H14N)3Bi2I9·H2O

The organic-inorganic metal halide perovskite materials have remarkable semiconductor and light absorption characteristics. It shows excellent application prospects in the fields of optoelectronics and temperature sensors. In this work, zero-dimensional lead-free (C6H14N)3Bi2I9·H2O single crystals were synthesized by conventional solvothermal reaction. The crystal structure was analyzed using single crystal X-ray diffraction (SXRD). (C6H14N)3Bi2I9·H2O was crystallized in the orthorhombic crystal system with the space group Pmn21. The material is stable for long-term storage under ambient conditions and shows a reversible thermochromic phenomenon. Through ultraviolet–visible–near-infrared (UV–vis–NIR) absorption analysis, the band gap of (C6H14N)3Bi2I9·H2O at room temperature is found to be 2.12 ​eV and it gradually decreases as the temperature increases. This indicates that the thermochromism is probably caused by charge transfer. The response of material to optical signals was also studied and the maximum value of the responsivity (R) and external quantum efficiency (EQE) at 275 ​nm could reach 11 ​mA/W and 2.4%, respectively. It suggests that the material has a potential for applications in photovoltaic devices.

Investigating on crystal structure, thermodynamic, and molecular dynamic of lead-free organic-inorganic hybrid [NH3(CH2)2NH3]ZnBr4 crystals

In this study, lead-free organic-inorganic hybrid [NH3(CH2)2NH3]ZnBr4 crystals were grown by slow evaporation and analyzed. The crystals showed orthorhombic structure with the P212121 space group, and the following lattice constants: a = 8.3818 (2) Å, b = 10.8880 (4) Å, c = 11.8175 (4) Å, and Z = 4. The crystals were stable up to 584 K, with two phase transitions at 468 K (TC1) and 503 K (TC2), as indicated by differential scanning calorimetry and differential thermal analysis. The structural environments of the atoms were analyzed by 1H and 13C NMR. On increasing the temperature, the spin-lattice relaxation time, T1ρ, decreased rapidly due to large energy transfer at high temperatures, as indicated by large thermal displacements of the 1H and 13C atoms of the cation. Additionally, the activation energy, Ea, at high and low temperatures was found to be 49.23 and 1.44 kJ/mol, respectively, for the molecular motion of 1H, and 37.93 and 2.13 kJ/mol, respectively, for that of 13C. Analyzing the physiochemical properties of [NH3(CH2)2NH3]ZnBr4 could facilitate its application in stable and environment-friendly solar cells.

Impact of organic amine cations on photoluminescence and magnetic properties in Dion-Jacobson hybrid manganese halide perovskites

A strenuous effort has been made to design multifunctional lead-free organic–inorganic hybrid (OIH) halide compounds, which are envisioned as next generation solar cell materials. However, it is challenging to design OIH halides that can exhibit both long-range magnetic ordering and high photoluminescence quantum yield (PLQY) since the dimensionality of the compounds has a contrasting effect on them. In this article, we have shown an approach to enhance PLQY in two-dimensional (2D) Heisenberg antiferromagnets by increasing the alkylene chain length of [H3N–(CH2)m–NH3]MnCl4 (m = 2, 3, and 4) compounds. All these compounds exhibit 2D layers of corner-sharing MnCl6 octahedra where the organic cations are intercalated between them. These compounds exhibit long-range antiferromagnetic ordering confirmed by the DC magnetic susceptibility and heat capacity measurements. The Néel temperature (TN) decreases with increasing the length of spacer cations due to a decrease in interlayer exchange interactions; however, interestingly, the lifetime of photoexcited electrons and PLQY enhances from 24 to 56 µs and 8% to 23%, respectively. Furthermore, the temperature-dependent photoluminescence measurements provide insight into thermal quenching and exciton binding energy. We believe this study can help to design new OIH halides with long-range magnetic ordering and high PLQY.

UV-VIS-NIR broadband flexible photodetector based on layered lead-free organic-inorganic hybrid perovskite.

The flexible photodetector is viewed as a research hotspot for numerous advanced optoelectronic applications. Recent progress has manifested that lead-free layered organic-inorganic hybrid perovskites (OIHPs) are highly attractive to engineering flexible photodetectors due to the effective overlapping of several unique properties, including efficient optoelectronic characteristics, exceptional structural flexibility, and the absence of Pb toxicity to humans and the environment. The narrow spectral response of most flexible photodetectors with lead-free perovskites is still a big challenge to practical applications. In this work, we demonstrate the flexible photodetector based on a novel (to our knowledge) narrow-bandgap OIHP of (BA)2(MA)Sn2I7, with achieving a broadband response across an ultraviolet-visible-near infrared (UV-VIS-NIR) region as 365-1064 nm. The high responsivities of 28.4 and 2.0 × 10-2 A/W are obtained at 365 and 1064 nm, respectively, corresponding to detectives of 2.3 × 1010 and 1.8 × 107 Jones. This device also shows remarkable photocurrent stability after 1000 bending cycles. Our work indicates the huge application prospect of Sn-based lead-free perovskites in high-performance and eco-friendly flexible devices.

Temperature symmetry breaking and properties of lead-free organic-inorganic hybrids: bismuth(III) iodide and antimony(III) iodide: (S(CH3)3)3[Bi2I9] and (S(CH3)3)3[Sb2I9

We have synthesized and characterized two novel lead-free organic-inorganic hybrid crystals: (S(CH3)3)3[Bi2I9] (TBI) and (S(CH3)3)3[Sb2I9] (TSI). Thermal DSC, TG, and DTA analyses indicate structural phase transitions (PTs) in both compounds; TBI undergoes two structural phase transitions at 314.2/314.8 K (cooling/heating) and at 181.5 K of first (I ↔ II) and second order (II ↔ III), respectively. The crystal structures of TBI are refined for phases I (325 K), II (200 K) and III (100 K). TBI exhibits ferroelastic properties since both PTs are accompanied by a change in the symmetry of crystals: P63/mmc → C2/c (I → II) and C2/c → P1̄ (II → III). The presence of a ferroelastic domain structure has been confirmed by optical observations. In turn, TSI also reveals two PTs: I ↔ II (at 303.9/304.1 K) and II ↔ III (212.9/221.4 K). To compare and obtain insight into the mechanism of the PTs of TBI, we have carried out temperature dependent single crystal X-ray diffraction studies. Additionally, to confirm the change in the dynamical states of molecules in PTs, dielectric measurements have been carried out between 100 K and 400 K in the frequency range of 200 Hz to 2 MHz. Moreover, the measurements of the 1H NMR spin-lattice relaxation time, T1, and a second moment, M2, of the 1H NMR line have been undertaken in the temperature range between 100 and 300 K.

Thermal-Induced Ferroelastics in Two Lead-Free Organic–Inorganic Hybrid Perovskites

Thermal-Induced Ferroelastics in Two Lead-Free Organic–Inorganic Hybrid Perovskites

Crystal structure, characterization and physical properties of lead-free organic–inorganic hybrid perovskites

Crystal structure, characterization and physical properties of lead-free organic–inorganic hybrid perovskites

New Lead-free Organic-Inorganic Hybrid Semiconductor Single Crystals for a UV-Vis-NIR Broadband Photodetector.

Organic-inorganic hybrid semiconducting (OIHS) materials, which can detect broader spectral regions, are highly desired in several applications including biomedical imaging, night vision, and optical communications. Although lead (Pb)-halide perovskites have reached a mature research stage, high toxicity of Pb hinders their large-scale viability. Tin (Sn)-based perovskites are the most common OIHS broadband light absorbers that replace toxic Pb; however, they are extremely unstable due to the notorious Sn2+ oxidation. Herein, a novel, non-toxic, and solution-processed millimeter-sized OIHS single crystal [Ga(C3H7NO)6](I3)3 has been grown at room temperature. Both the absorption measurement and density functional theory calculations have confirmed a narrow indirect band gap of 1.32 eV. The corresponding photodetector based on this single crystal demonstrated excellent performance including an ultraviolet-visible-near infrared (UV-vis-NIR) response between 325 and 1064 nm, fast response time (trise/tdecay = 3.8 ms/5.4 ms), and profound air storage stability (41 h), thus outperforming most common photodetectors based on Sn-based perovskites. This work not only provides a profound understanding of this novel organic-inorganic single-crystal material but also demonstrates its great potential to realize the high-performance UV-vis-NIR broadband photodetectors.

Zero-Dimensional (Piperidinium)2MnBr4: Ring Puckering-Induced Isostructural Transition and Strong Electron-Phonon Coupling-Mediated Self-Trapped Exciton Emission.

We report on the synthesis, structure, and photophysical properties of a lead-free organic-inorganic hybrid halide, (Piperidinium)2MnBr4 (PipMBr). It crystallizes in a monoclinic P21/n structure, with isolated MnBr4 tetrahedra representing a zero-dimensional compound. It undergoes a reversible isostructural transition at 422/417 K in the heating/cooling cycle owing to the hydrogen-bonding rearrangement mediated by ring puckering of piperidinium cations. This compound exhibits green emission with a photoluminescence quantum yield of 51%. Interestingly, strong electron-longitudinal optical phonon coupling with γLO of 237 meV is evidenced from the broadening of the temperature-dependent emission linewidth and the Raman spectrum. Such strong electron-phonon coupling and a relatively low Debye temperature (137 K) suggest the self-trapped exciton emission in this compound.

2D lead-free organic–inorganic hybrid exhibiting dielectric and structural phase transition at higher temperatures

A novel switchable molecular dielectric material [3-3-difluorocyclobutylammonium]2CdCl4 was synthesized. It shows a reversible phase transition at 353.95 K and rapid switching and reversibility between high and low dielectric states for several cycles.

Effects of Halogen Substitutions on Photoelectric Properties and Stability of Two-Dimensional Lead-Free Organic-Inorganic Hybrid Double Perovskite (C6h16n2)2agbix8.H2o(X=I, Br, Cl) with a Dion-Jacobson Structure

Effects of Halogen Substitutions on Photoelectric Properties and Stability of Two-Dimensional Lead-Free Organic-Inorganic Hybrid Double Perovskite (C6h16n2)2agbix8.H2o(X=I, Br, Cl) with a Dion-Jacobson Structure

Crystal structure and thermochromic behavior of the quasi-0D lead-free organic-inorganic hybrid compounds (C7H9NF)8M4I16 (M = Bi, Sb)

The quasi 0D lead-free thermochromic organic-inorganic hybrid single crystals (C7H9NF)8M4I16 (M = Bi, Sb) were synthesized by a conventional solvothermal reaction method. The crystal structures were analyzed using single crystal X-ray diffraction (SXRD). Interestingly, as the temperature increases, the (C7H9NF)8M4I16 (M = Bi, Sb) crystals exhibit a peculiar thermochromic phenomenon. In order to explore the phenomenon of thermochromism, temperature dependent ultraviolet−visible-near-infrared (UV–vis–NIR) absorption spectra were measured. The bandgaps of (C7H9NF)8Sb4I16 and (C7H9NF)8Bi4I16 at room temperature are 2.34 eV and 2.1 eV, respectively, and they gradually decrease as the temperature increases. Combined with ab initio molecular dynamics (AIMD), the reduction of the bandgap at higher temperature and the occurrence of thermochromism could be caused by the stronger electronic activity (thermal excitation). The thermochromic characteristics of these low-dimensional organic-inorganic hybrid metal halides will provide alternative materials for smart windows temperature sensors, visual thermometers, and daylight control glasses and beyond.

Self-Trapped Exciton Emission in a Zero-Dimensional (TMA)2SbCl5·DMF Single Crystal and Molecular Dynamics Simulation of Structural Stability.

Lead-free lower-dimensional organic-inorganic metal halide materials have recently triggered intense research because of their excellent photophysical properties and chemical stability. Herein, we report a novel zero-dimensional (0D) organic-inorganic hybrid single crystal (TMA)2SbCl5·DMF (TMA = N(CH3)3, DMF= HCON(CH3)2), which exhibits typical self-trapped exciton (STE) emission with an efficient yellow emission at 630 nm and high photoluminescence quantum yield (PLQY) of 67.2%. The dual STE emission is attributed to the singlet and triplet STEs in inorganic [SbCl5]2-, respectively. Further, an ab initio molecular dynamics simulation was performed to estimate the stability of crystal structure at room temperature. The calculated excited-state structure indicates that the deformation parameter (Δd) of the excited-state structure is larger than that of the ground state, illustrating the origin of a large Stokes shift. These results indicate that these new 0D lead-free organic-inorganic hybrid metal halides are promising luminescent materials for optoelectronic applications.

(C5H9N2)[BiI4]: A One-Dimensional Bismuth-Based Organic–Inorganic Hybrid Material for Fast Rhodamine B Degradation Under Dark Condition

Lead-free organic–inorganic hybrid materials have attracted wide interest due to their excellent optoelectronic and photovoltaic properties. Herein, we synthesized a Bi-based hybrid material with one-dimensional (1D) Bi-I anionic chains, namely, (C5H9N2)[BiI4] (1) by solvothermal method. Single-crystal X-ray diffraction analysis reveals that it crystallizes in monoclinic space group of C2/c with the cell parameters a = 15.539(13) A, b = 13.860(12) A, c = 7.789(6) A, β = 117.02(2)o, V = 1494(2) A3, and Z = 4, which is composed of protonated 1,3-dimethylimidazolium cations and one-dimensional (1D) [BiI4]∞− chains interconnected via edge-sharing μ2-I. This compound exhibits fast degradation of rhodamine B (RhB) at room temperature under dark condition.

Highly Efficient Cool-White Photoluminescence of (Gua)3Cu2I5 Single Crystals: Formation and Optical Properties.

Zero-dimensional lead-free organic-inorganic hybrid metal halides have drawn attention as a result of their local metal ion confinement structure and photoelectric properties. Herein, a lead-free compound of (Gua)3Cu2I5 (Gua = guanidine) with a different metal ion confinement has been discovered, which possesses a unique [Cu2I5]3- face-sharing tetrahedral dimer structure. First-principles calculation demonstrates the inherent nature of a direct band gap for (Gua)3Cu2I5, and its band gap of ∼2.98 eV was determined by experiments. Worthy of note is that (Gua)3Cu2I5 exhibits a highly efficient cool-white emission peaking at 481 nm, a full-width at half-maximum of 125 nm, a large Stokes shift, and a photoluminescence quantum efficiency of 96%, originating from self-trapped exciton emission. More importantly, (Gua)3Cu2I5 single crystals have a reversible thermoinduced luminescence characteristic due to a structural transition scaled by the electron-phonon coupling coefficients, which can be converted back and forth between cool-white and yellow color emission by heating or cooling treatment within a short time. In brief, as-synthesized (Gua)3Cu2I5 shows great potential for application both in single-component white solid-state lighting and sensitive temperature scaling.

Lead-free organic–inorganic hybrid semiconductors and NLO switches tuned by dimensional design

Two organic–inorganic hybrid materials exhibit functional regulation by introducing homochiral cations and different reagent ratios.