Hybrid Organic-inorganic Halide Research Articles

A green and facile synthesis of lead-free hybrid organic-inorganic bismuth halides quantum dots for nanophotonics applications

There has been an urgent need to eliminate toxic lead from the popular halide perovskite for various photonics and optoelectronics applications. This is added by the use of dangerous and environment unfriendly chemical during the wet synthesis route. Herein we demonstrate the synthesis of lead-free halide perovskite – (PhA)BiI4 (phenylammonium tetraiodobismates) and PhABiBr4 (phenylammonium tetrabromobismates) quantum dots (QDs) in room ambient environment using eco-friendly solvent - Ethanol. FESEM-EDX analysis of PhABiI4 and PhABiBr4 confirm the 1:4 atomic ratio of Bi:I and Bi:Br. As revealed by HRTEM, the as-prepared PhABiI4 indicate the formation of QDs with sizes smaller than 10 nm. Similar morphology was observed for PhABiBr4 QDs, but smaller in size compared to PhABiI4. High optical transparency was observed, and optical bandgap was measured for both PhABiI4 and PhABiBr4 QDs at 2.25 eV for and 3.07 eV, respectively. Chromaticity studies under 365 nm irradiation reveal a bright cyan emission for the PhABiI4 and bright blue emission for the PhABiBr4 QDs. Large magnitude of nonlinear optical susceptibility, |χ(3)| were calculated in the order of 10−6 esu. The green and facile synthesis approach reported here represents an alternate avenue for the new applications of Bi-based perovskite particularly towards the next-generation nanophotonics technologies.

High quality quasi-two-dimensional organic–inorganic hybrid halide perovskite film for high performance photodetector

Two-dimensional (2D) Ruddlesden–Popper perovskites have attracted extensive attention in photodetectors (PDs) due to their exceptional optoelectronic properties. The performances of PDs show extremely strong dependence on defects in 2D perovskites. Herein, high quality and less defective BA2FAPb2I7 perovskite films were obtained by a simple one-step spin coating method with rare earth doping assisted crystal growth. Furthermore, BA2FAPb2I7 perovskite films were used as photoresponsive materials to fabricate architectural simplicity photoconductor PDs. Under 405 nm laser illumination, the PDs show remarkable balance detect properties with a low dark current of 5.1 × 10−11 A, a large on/off ratio of 2.2 × 105, a high responsivity (R) of 4.51 A/W, an outstanding detectivity Dshot* of 4.31 × 1013 Jones, and a response speed of 80 μs/76 μs. The R and Dshot* of the PDs are outstanding in the reported quasi-2D perovskite PDs with the same structure. Our work not only paves an indubitably feasible way for fabrication of quasi-2D perovskite PDs via improving their natural material properties but also provides a clear direction for further enhancing the performance of other perovskites optoelectronics.

Stable Organic Antimony Halides with Near‐Unity Photoluminescence Quantum Yield for X‐Ray Imaging

AbstractX‐ray imaging technology has been widely used in the fields of environmental monitoring, safety inspection, nondestructive examination, space exploration, and medical diagnosis, among which scintillation materials play a vital role in indirectly converting X‐ray to visible photons. Here, a zero‐dimensional organic–inorganic hybrid halide C50H44P2SbCl5 crystal is prepared via a facile antisolvent precipitation method at room temperature. The single crystal of C50H44P2SbCl5 displays a strong yellow broadband emission centered at 592 nm with a near‐unity photoluminescence quantum yield of 98.42%. Importantly, C50H44P2SbCl5 crystals show great environmental stability and irradiation stability. Radioluminescence characterization indicates that C50H44P2SbCl5 crystals exhibit a good linear response to X‐ray dose rates along with an excellent light yield of 44 460 photons MeV−1, surpassing that of commercial inorganic LuAG:Ce scintillator. The spatial resolution of the C50H44P2SbCl5‐based scintillating screen is determined to be 8.2 lp mm−1. In conjunction with polymer thin film, the excellent scintillating feature of organic–inorganic hybrid halides offers exciting opportunities for achieving high‐quality flexible X‐ray imaging.

Real-time observation of the buildup of polaron in α-FAPbI3

The formation of polaron, i.e., the strong coupling process between the carrier and lattice, is considered to play a crucial role in benefiting the photoelectric performance of hybrid organic-inorganic halide perovskites. However, direct observation of the dynamical formation of polarons occurring at time scales within hundreds of femtoseconds remains a technical challenge. Here, by terahertz emission spectroscopy, we demonstrate the real-time observation of polaron formation process in FAPbI3 films. Two different polaron resonances interpreted with the anharmonic coupling emission model have been studied: P1 at ~1 THz relates to the inorganic sublattice vibration mode and the P2 at ~0.4 THz peak relates to the FA+ cation rotation mode. Moreover, P2 could be further strengthened than P1 by pumping the hot carriers to the higher sub-conduction band. Our observations could open a door for THz emission spectroscopy to be a powerful tool in studying polaron formation dynamics in perovskites.

Elucidating Structure-Property Correlation in Perovskitoid and Antiperovskite Piperidinium Manganese Chloride.

In the world of semiconductors, organic-inorganic hybrid (OIH) halide perovskite is a new paradigm. Recently, a zealous effort has been made to design new lead-free perovskite-like OIH halides, such as perovskitoids and antiperovskites, for optoelectronic applications. In this context, we have synthesized a perovskitoid compound (Piperidinium)MnCl3 (compound 1) crystallizing in an orthorhombic structure with infinite one-dimensional (1D) chains of MnCl6 octahedra. Interestingly, this compound shows switchable dielectric property governed by an order-disorder structural transition. By controlling the stoichiometry of piperidine, we have synthesized an antiperovskite (Piperidinium)3Cl[MnCl4] (compound 2), the inverse analogue of a perovskite, consisting of zero-dimensional (0D) MnCl4 tetrahedra. This type of organic-inorganic hybrid antiperovskite halide is unique and scarce. Such a dissimilarity in lattice dimensionality and Mn2+ ion coordination ensues fascinating photophysical and magnetic properties. Compound 1 exhibits red emission with a photoluminescence quantum yield (PLQY) of ∼28%. On the other hand, the 0D antiperovskite compound 2 displays green emission with a higher PLQY of 54.5%, thanks to the confinement effect. In addition, the dimensionality of the compounds plays a vital role in the exchange interaction. As a result, compound 1 shows an antiferromagnetic ground state, whereas compound 2 is paramagnetic down to 1.8 K. This emerging structure-property relationship in OIH manganese halides will set the platform for designing new perovskites and antiperovskites.

Achieving Near-unity Photoluminescence Quantum Yields in Organic-Inorganic Hybrid Antimony (III) Chlorides with the [SbCl5 ] Geometry.

Hybrid organic-inorganic antimony halides have attracted increasing attention due to the non-toxicity, stability, and high photoluminescence quantum yield (PLQY). To shed light on the structural factors that contribute to the high PLQY, five pairs of antimony halides with general formula A2 SbCl5 and A2 Sb2 Cl8 are synthesized via two distinct methods and characterized. The A2 SbCl5 type adopts square pyramidal [SbCl5 ] geometry with near-unity PLQY, while the A2 Sb2 Cl8 adopts seesaw dimmer [Sb2 Cl8 ] geometry with PLQY≈0 %. Through combined data analysis with the literature, we have found that A2 SbCl5 series with square pyramidal geometry generally has much longer Sb⋅⋅⋅Sb distances, leading to more expressed lone pairs of SbIII . Additional factors including Sb-Cl distance and stability of antimony chlorides may also affect PLQY. Our targeted synthesis and correlated insights provide efficient tools to precisely form highly emissive materials for optoelectronic applications.

Spacer-Dependent and Pressure-Tuned Structures and Optoelectronic Properties of 2D Hybrid Halide Perovskites.

Compared with their 3D counterparts, 2D hybrid organic-inorganic halide perovskites (HOIPs) exhibit enhanced chemical stabilities and superior optoelectronic properties, which can be further tuned by the application of external pressure. Here, we report the first high-pressure study on CMA2PbI4 (CMA = cylcohexanemethylammonium), a 2D HOIP with a soft organic spacer cation containing a flexible cyclohexyl ring, using UV-visible absorption, photoluminescence (PL) and vibrational spectroscopy, and synchrotron X-ray microdiffraction, all aided with density functional theory (DFT) calculations. Substantial anisotropic compression behavior is observed, as characterized by unprecedented negative linear compressibility along the b axis. Moreover, the pressure dependence of optoelectronic properties is found to be in strong contrast with those of 2D HOIPs with rigid spacer cations. DFT calculations help to understand the compression mechanisms that lead to pressure-induced bandgap narrowing. These findings highlight the important role of soft spacer cations in the pressure-tuned optoelectronic properties and provide guidance to the design of new 2D HOIPs.

Rational Design of Non-Centrosymmetric Hybrid Halide Perovskites.

Structural non-centrosymmetry in semiconducting organic-inorganic hybrid halide perovskites can introduce functionalities like anomalous photovoltaics and nonlinear optical properties. Here we introduce a design principle to prepare Pb- and Bi-based two- and one-dimensional hybrid perovskites with polar non-centrosymmetric space groups. The design principle relies on creating dissimilar hydrogen and halogen bonding non-covalent interactions at the organic-inorganic interface. For example, in organic cations like I-(CH2)3-NH2(CH3)+ (MIPA), -CH3 is substituted by -CH2I at one end, and -NH3+ is substituted by -NH2(CH3)+ at the other end. These substitutions of two -H atoms by -I and -CH3 reduce the rotational symmetry of MIPA at both ends, compared to an unsubstituted cation, for example, H3C-(CH2)3-NH3+. Consequently, the dissimilar hydrogen-iodine and iodine-iodine interactions at the organic-inorganic interface of (MIPA)2PbI4 2D perovskites break the local inversion symmetries of Pb-I octahedra. Owing to this non-centrosymmetry, (MIPA)2PbI4 displays visible to infrared tunable nonlinear optical properties with second and third harmonic generation susceptibility values of 5.73 pm V-1 and 3.45 × 10-18 m2 V-2, respectively. Also, the single crystal shows photocurrent on shining visible light at no external bias, exhibiting anomalous photovoltaic effect arising from the structural asymmetry. The design strategy was extended to synthesize four new non-centrosymmetric hybrid perovskite compounds. Among them, one-dimensional (H3N-(CH2)3-NH(CH3)2)BiI5 shows a second harmonic generation susceptibility of 7.3 pm V-1 and a high anomalous photovoltaic open-circuit voltage of 22.6 V.

Linear optical afterglow and nonlinear optical harmonic generation from chiral tin(IV) halides: the role of lattice distortions.

The striking chemical variability of hybrid organic-inorganic metal halides (HOMHs) endows them with fascinating optoelectronic properties. The inorganic skeletons of HOMHs are often flexible and their lattice deformations could serve as an effective factor for enabling the functionalities of HOMHs. Here, the linear and nonlinear optical properties of zero-dimensional (0D) tin(IV) halides have been tuned by structural distortion facilitated by the chiral amines. Enantiopure α-methylbenzyl ammoniums (XMBA, X = Cl, F) effectively transfer their chirality to the inorganic scaffolds when forming the tin(IV) halides, which enables polar arrangements in their crystals and leads to outstanding second-order nonlinear optical performances. In contrast, the racemic mixture of R- and S-FMBA results in the formation of HOMHs with room temperature phosphorescence. The lower lattice deformation in (rac-FMBA)2SnCl6 restrains the non-radiative decay from electron-phonon coupling and facilitates the photoluminescence. Meanwhile, the marked π-π interaction stabilizes the T1 state for phosphorescent emission. These distinct linear and nonlinear optical properties denote the important role that the lattice distortion plays in tuning the optical properties of low-dimensional HOMHs, and offer a promising perspective of 0D tin(IV) halides for applications in optoelectronic materials and devices.

Performance and stability enhancement of perovskite photodetectors by additive and interface engineering using a dual-functional PPS zwitterion.

Hybrid organic-inorganic metal halide perovskites (HOIPs) have gained significant research interest due to their tunable optoelectronic properties and ease of fabrication. Enhancing the stability and efficiency of perovskite materials can be achieved through the passivation of defective surfaces and the improvement of interfacial properties. In this study, we introduce a zwitterionic compound, PPS (3-(1-pyridinio)-1-propanesulfonate), as a bifunctional material that serves as an additive and an interlayer. Incorporating PPS into the perovskite film effectively reduces both positively and negatively charged defects, leading to improved surface morphology and a reduction in undesired charge carrier recombination. Additionally, the formation of a PPS interlayer on SnO2 improves the SnO2/perovskite interfacial characteristics, thereby enhancing charge carrier extraction. As a result, the photodetector exhibits a low dark current of 6.05 × 10-11 A, an excellent responsivity of 5.93 A W-1, a detectivity of 1.51 × 1013 J, and an on/off ratio of 1.2 × 104 under open-air conditions. Moreover, the device demonstrates outstanding stability, retaining 80% of its original responsivity in an ambient environment. This work highlights the great potential of dual-functional materials for defect passivation in future optoelectronic devices, emphasizing the importance of surface modification and interface engineering for improved performance and stability.

Second harmonic generation from symmetry breaking stimulated by mixed organic cations in zero-dimensional hybrid metal halides.

Mixing cations with different chemical properties to induce the generation of asymmetric structures is a new approach for tuning the optical properties of hybrid organic-inorganic metal halides (HOIMHs). In this study, zero-dimensional (C9N3H15)(C9H13SO)MBr6 (M = Bi/Sb, [C9N3H15]2+ = [(C4N2H10)(C5NH5)]2+ and [C9H14SO]+ = [CH3(C6H4)OS(CH3)2]+) are synthesized. Two different cations cause both compounds to crystallize in the polar space group P212121, thus resulting in significant phase matchable second harmonic generation under a 1064 nm laser excitation. Thus, (C9N3H15)(C9H13SO)BiBr6 and (C9N3H15)(C9H13SO)SbBr6 exhibit intensities that are approximately 1.8 and 1.7 times that of KH2PO4, respectively. The results of density functional theory calculations show that both (C9N3H15)(C9H13SO)BiBr6 and (C9N3H15)(C9H13SO)SbBr6 exhibit direct bandgaps of 2.95 and 2.81 eV, respectively. Additionally, because of the distortion of the inorganic octahedra, (C9N3H15)(C9H13SO)SbBr6 exhibited bright yellow emission at room temperature, which is attributed to ns2 fluorescence emission. We believe that the symmetry of the HOIMH crystal structure can be broken by introducing spatially differentiated bifunctional organic cations, which consequently enables even-order nonlinear activities.

Solution-Processed Hybrid Europium (II) Iodide Scintillator for Sensitive X-Ray Detection.

Lead halide perovskite nanocrystals have recently demonstrated great potential as x-ray scintillators, yet they still suffer toxicity issues, inferior light yield (LY) caused by severe self-absorption. Nontoxic bivalent europium ions (Eu2+) with intrinsically efficient and self-absorption-free d-f transition are a prospective replacement for the toxic Pb2+. Here, we demonstrated solution-processed organic-inorganic hybrid halide BA10EuI12 (BA denotes C4H9NH4+) single crystals for the first time. BA10EuI12 was crystallized in a monoclinic space group of P21/c, with photoactive sites of [EuI6]4- octahedra isolated by BA+ cations, which exhibited high photoluminescence quantum yield of 72.5% and large Stokes shift of 97 nm. These properties enable an appreciable LY value of 79.6% of LYSO (equivalent to ~27,000 photons per MeV) for BA10EuI12. Moreover, BA10EuI12 shows a short excited-state lifetime (151 ns) due to the parity-allowed d-f transition, which boosts the potential of BA10EuI12 for use in real-time dynamic imaging and computer tomography applications. In addition, BA10EuI12 demonstrates a decent linear scintillation response ranging from 9.21 μGyair s-1 to 145 μGyair s-1 and a detection limit as low as 5.83 nGyair s-1. The x-ray imaging measurement was performed using BA10EuI12 polystyrene (PS) composite film as a scintillation screen, which exhibited clear images of objects under x-ray irradiation. The spatial resolution was determined to be 8.95 lp mm-1 at modulation transfer function = 0.2 for BA10EuI12/PS composite scintillation screen. We anticipate that this work will stimulate the exploration of d-f transition lanthanide metal halides for sensitive x-ray scintillators.

A first-principles study of quaternary thioiodides for stable lead-free solar cells

Organic–inorganic hybrid halide perovskites have recently attracted enormous interest as photovoltaic materials because of their superior solar cell performance and straightforward fabrication.

Design and Development of Hybrid Halide Perovskites in Laser Devices

Organic-inorganic hybrid halide perovskite is a significant semiconductor material in photonics. Their outstanding optoelectronic characteristics have been reported, increasing energy conversion efficiency of perovskite solar battery by up to 25.5%, which is expected to be major competitors in silicon industry. According to the fundamentals of physics, a viable candidate for a light emitter must really be a superior direct band gap material. Even though there are a lot of papers on perovskite-based light emitting devices in this area, the corresponding laser devices are still lack of research. Here, since the first publication of lasing in hybrid perovskites in the 1990s, great effort has been made especially in 2014. Halide perovskites have the potential to revolutionize the nanophotonics field due to their solution-processed gain medium, almost defect-free semiconductor formation, high luminous efficiency, flexibility of nanostructure, excellent stability, and wide wavelength tunability. This article highlights the important researches on the optical gain from diverse hybrid halide perovskite material and the future challenges of lasing.

Photo-synaptic properties of CH3NH3Pb1-xMnxBr2x+1 hybrid perovskite thin film-based artificial synapse

With the increasing demands on unstructured data processing, a system emulating the human nervous system has garnered great attention as an alternative to the von-Neumann architecture due to low power consumption and parallel data processing. To realize the neuromorphic computing, the artificial electronic synapse, neuron device and architecture have been investigated using various materials and devices. In this regard, in addition to electrical-responsive synaptic devices, photoresponsive synapse devices are attracting attention due to photoresponse with high bandwidth, low power consumption, and low current crosstalk. Espicially, the organic-inorganic hybrid halide perovskites (OIHPs) are promising materials for photodevices due to broad optical absorption, low exciton binding energy, fast charge transport properties, and tunable bandgap. The OIHPs have been implemented to demonstrate the photo-stimulated synaptic functions, however, most OIHPs contain toxic lead cations, limiting their widespread application. In this study, we investigated the light-stimulated photosynaptic characteristics based on OIHPs synthesized with Mn2+ (CH3NH3Pb1-xMnxBr2x+1) that could substitute non-desirable Pb-based perovskite. The Mn2+-based OIHPs photosynapstor successfully emulated the essential synaptic characteristics including excitatory post-synaptic current, pulse-paired facilitation, post-tetanic potentiation, transition from short-term plasticity to long-term plasticity, forgetting curve, and spike-timing dependent plasticity.

High-pressure investigations in CH3NH3PbX3 ( X = I, Br, and Cl): Suppression of ion migration and stabilization of low-temperature structure

Hybrid organic-inorganic halide perovskites represent a promising next-generation photovoltaic material with drawbacks for structure stability and composition concerns. Demonstrations of ion migration and molecular dynamics suggest room for structural contraction and subsequent property adjustments. Here, we deploy dielectric and infrared spectroscopy under external pressure to probe the full structural phase diagram and dielectric response of methylammonium lead halide perovskites ${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}\mathrm{Pb}{X}_{3}$ ($X\phantom{\rule{4pt}{0ex}}=$ I, Br, or Cl). Ion migration can be fully suppressed by pressure beyond 4 GPa. The low-temperature orthorhombic phase transition can be gradually enhanced and stabilized at ambient conditions with increasing pressure. A slow relaxation mode, presumably the motion of the ${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}^{+}$ cation, is observed at lower pressure and is absent in the orthorhombic phase for every halide.

Efficient photosensitized singlet oxygen generation in two-dimensional perovskite nanosheets via energy transfer

Two-dimensional (2D) organic-inorganic hybrid halide perovskites have gained extensive attention in photovoltaics, photodetectors and light-emitting diodes owing to their unique optoelectronic properties and superior stability compared with their three-dimensional (3D) counterparts. However, 2D perovskites have rarely been applied for photochemical conversion applications. Herein, a series of 2D BA2MAn-1PbnBr3n+1 perovskite nanosheets have been synthesized through a facile, ligand-free precipitation (LFP) method at room temperature. Using the specific chemical trapping techniques, we show for the first time that the 2D perovskite nanosheets can effectively generate photosensitized singlet oxygen (1O2) via energy transfer from triplet excitons to molecular oxygen in non-polar solvent. Based on this discovery, the as-prepared BA2PbBr4 and BA2MAPb2Br7 nanosheets successfully catalyze the ENE reaction and 1,2-addition reaction between olefin and singlet oxygen under visible light. Our study is anticipated to develop and demonstrate new mechanisms for 2D halide perovskite materials in photodynamic therapy and photocatalytic applications.

Water-driven Successive Structural Transformation in a Two-Dimensional (2D) Lead-Free Hybrid Double Perovskite.

Hybrid organic-inorganic halide perovskites (HOIPs) have received continued interest for their structure diversity and potential application in optoelectronic, solar cells, nonlinear optics (NLO), and ferroelectrics. Structural symmetry breaking induced by water molecules in single-crystal-to-single-crystal (SCSC) transformations is beneficial to develop ferroelectrics or second-harmonic generation (SHG) materials. Along this line, a water-containing two-dimensional (2D) double perovskite, (C6H16N2)2AgBiBr8·H2O (1), was prepared. Acentric 1 suffered a twice SCSC transformation when subjected to dehydration and rehydration, where the new centric (C6H16N2)2AgBiBr8 (2) and acentric (C6H16N2)2AgBiBr8·0.5H2O (3) were generated. In contrast to the irreversible transformation from 1 to 2 (symmetry: P21 → Pmna), it is prominent that the reversible conversion of centric 2 to acentric 3 (symmetry: Pmna ↔ P21212). The result validated the effect of guest water on inducing structural transformation and symmetry breaking of 2D perovskites, inspiring further explorations on water-involved 2D materials.

Large grain size with reduced non-radiative recombination in potassium incorporated methylammonium-free perovskite solar cells

Organic–inorganic hybrid halide perovskites are widely considered to be one the most promising material in photovoltaic technology, the use of this semiconductor as absorbent layer in solar cells has attracted considerable interest due to their excellent properties. It has been reported that the incorporation of potassium ion is a powerful strategy to tune the perovskites properties, notwithstanding there has been some disagreement regarding the role of this monovalent alkali metal within the perovskite structure. Here, we investigated the impact of K + on the film properties and photovoltaic performance in double cation perovskite solar cells Cs 0.1 FA 0.9 PbI 3 . Our results show that K + intervenes in the crystallization process inducing the extraction of non-reactive PbI 2 from the bulk, resulting in a notable enhancement in morphology and reduced non-radiative recombination. The solar cells fabricated with 3% of K + content achieve a PCE of 19.3%, showing a significative improvement in J sc , V oc and stability values compared with control devices. • Large grain size with reduced non-radiative recombination. • Potassium incorporated methylammonium-free perovskite. • K + incorporation improves significatively the performance of perovskite solar cells.

Spin Selectivity in Chiral Hybrid Cobalt Halide Films with Ultrasmooth Surface.

Introducing chirality into low-dimensional hybrid organic-inorganic halides (HOIHs) creates brand-new opportunities for HOIHs in spintronics and spin-related optoelectronics owing to chirality-induced spin selectivity (CISS). However, preparing smooth films of low-dimensional HOIHs with small roughness is still a great challenge due to the hybrid and complex crystal structure, which severely inhibits their applications in spintronic devices. Exploring new lead-free chiral HOIHs with both efficient spin selectivity and excellent film quality is urgently desired. Here, cobalt-based chiral metal halide crystals (R/S-NEA)2 CoCl4 constructed by 0D [CoCl4 ] tetrahedrons and 1-(1-naphtyl)ethylamine (NEA) are synthesized. The orderly configuration of NEAmolecules stabilized by noncovalent CH···π interaction endows (NEA)2 CoCl4 with good film-forming ability. (NEA)2 CoCl4 films exhibit strong chiroptical activity (gCD ≈ 0.05) and significant spin-polarized transport (CISS efficiency up to 90%). Furthermore, ultrasmooth films (roughness ∼ 0.3nm) with enhanced crystallinity can be achieved by incorporating tiny amount tris(8-oxoquinoline)aluminum that has analogous conjugated structure to NEA. The realization of highly efficient spin selectivity and sub-nanometer roughness in lead-free chiral halides can boost the practical process of low-dimensional HOIHs in spintronics and other fields.