Low-dimensional Halide Perovskites Research Articles

Low-dimensional halide perovskites for advanced electronics

Halide perovskites are gaining prominence as promising materials for future electronic applications, primarily due to their unique properties including long carrier diffusion lengths, tunable bandgap, facile synthesis, and cost efficiency. However, polycrystalline halide perovskite thin films, which have been widely studied to date, have significant drawbacks including uncontrollable grain boundaries and instability issues. Recently, low-dimensional halide perovskites (LD HPs) offer enhanced stability and adaptable morphologies, making them attractive candidates for next-generation electronics beyond optoelectronics. This review comprehensively explores recent advancements in LD HP-based electronics, covering structural characteristics, synthesis methods tailored to different dimensions, and diverse applications. Furthermore, the impressive performance demonstrated by LD HPs in electronic applications including resistive random-access memory, advanced transistors, and neuromorphic computing hardware is discussed. Finally, the review outlines the challenges and perspectives required to scale up LD HP-based advanced electronics for commercial production, offering valuable insights for researchers venturing into the realm of new materials for advanced electronics.

Effect of dimensional confinement on the memristive properties of the perovskite-inspired novel CuxAgBiI4+x halide compound

Low dimensional halide perovskite materials have shown significant performance enhancement in memristor devices. In search of highly stable and robust perovskites, several perovskite-inspired structures are proposed. This present study demonstrates the fabrication of novel lead-free all-inorganic CuxAgBiI4+x (x = 1 or 2) as the active material sandwiched between gold and indium doped tin oxide electrodes. Initial studies revealed that the memristor devices consisting of two-dimensional Cu2AgBiI6 have higher current on/off ratio as compared to the three-dimensional CuAgBiI5. This is ascribed to the elevated Schottky barrier at the Au/Cu2AgBiI6 interface as suggested by ultraviolet photoelectron spectroscopy, which resulted low current in the high resistance state (HRS) of the device. Kelvin probe force microscopy shows that the charge accumulation property is similar in both the materials although the CuAgBiI5 possesses less vacancies. However, the high switching window of the Cu2AgBiI6-based device succeeded in retaining the stable on/off ratio in the cycling endurance. Artificial synaptic characterizations have been carried out in the Cu2AgBiI6 based device due to low HRS current. The device could mimic paired-pulsed facilitation, transition from short-term to long-term potentiation and thus establishes the fact that low dimensional perovskite-type materials possess great potential for memristor application.

Large-Area Transparent Antimony-Based Perovskite Glass for High-Resolution X-ray Imaging.

Nonlead low-dimensional halide perovskites attract considerable attention as X-ray scintillators. However, most scintillation screens exhibit pronounced light scattering, which detrimentally reduces the quality of X-ray imaging. Herein, we employed a simple and straightforward solvent-free melt-quenching method to fabricate a large-area zero-dimension (0D) antimony-based perovskite transparent medium, namely (C20H20P)2SbCl5 (C20H20P+ = ethyltriphenylphosphine). The transparency is due to the large steric hindrance of C20H20P+, which hinders the formation of crystals during the quenching process, thus forming a glass with low refractive index and uniform structure. This medium exhibits a high transmittance exceeding 80% in the range of 450-800 nm and shows a large Stokes shift of 245 nm, thereby minimizing light scattering, mitigating self-absorption, and enhancing the clarity of X-ray imaging. Moreover, it exhibits a high radioluminescence light yield of ∼12,535 photons MeV-1 and displays a high X-ray spatial resolution of 30 lp mm-1 owing to its high transparency. This study presents an alternative candidate for achieving high-quality X-ray detection and extends the applicability of transparent perovskite scintillators.

Low-dimensional halide perovskite/PVDF nanocomposite with enhanced piezoelectricity as flexible biomechanical energy harvester

Sustainable energy harvesting is the need of the hour, and piezoelectric nanogenerators (PENG) offer tremendous opportunities in this field. We have investigated the mechanical energy harvesting applications of a nanocomposite comprising a low-dimensional halide perovskite (HP) and polyvinylidene fluoride (PVDF). Cs4PbBr6 HP was prepared using mechanochemical synthesis, and a composite film of PVDF with Cs4PbBr6 was utilized as the PENG to scavenge energy from day-to-day human biomechanical activities. The properties and output results of the fabricated devices with changing weight percentages (wt.%) of HP used as nanofillers in the PVDF matrix are compared to those of a pure PVDF. A 6 wt.% concentration of Cs4PbBr6 induces the composite's electroactive β-phase to around 87%. The polarization hysteresis (P-E) loop measurement reveals a remanent polarization of 0.31 µC/cm2. The measured piezoelectric coefficient (d33) is about ⁓12 pm/V, and the piezoelectric amplitude is ∼500 pm for the optimized PENG at the maximum applied bias of ±30 V. The device shows an instantaneous output voltage of ⁓90 V, a current of ⁓3.8 μA, and power of ⁓80 µW across a 5 MΩ resistor. Simple daily human activities like finger tapping, leg-toe pressing, finger bending, heel pressing, and walking are used to generate output voltages using PENG with prospective usage in powering portable electronic devices. The output AC voltage of the device is employed to charge a 10 µF capacitor up to ∼3.5 V and shows exceptional stability over long cycles. The output power generated is adequate for lighting commercial LEDs without any external input. The Cs4PbBr6/PVDF composite films thus demonstrate significant potential to be deployed as high-performance, portable, and wearable mechanical energy harvesting devices.

Regulating The Electronic Configuration of Low-Dimensional Hybrid Perovskites via Organic Cations for Self-Powered Ultraviolet Photodetectors.

Ultraviolet photodetectors (UPDs) based on low-dimensional halide perovskites have undergone rapid development. Here, regulation ofthe electronic configuration of low-dimensional hybrid perovskites are reported via organic cations for self-powered UPDs. For the first time, it is determine that the rational design of organic cation phenyl alkylammonium can effectively prevent phonon scattering thus increasing charge carrier extraction in low dimensional lead chlorine perovskite thin-films. As a result, the exciton-binding energy can be reduced to 62.91meV in (PMA)2 PbCl4 perovskite films with a charge-carrier mobility of 0.335cm2 V-1 s-1 . The fabricated (PMA)2 PbCl4 -based self-powered UPDs has achieved a high detectivity of 6.32 × 1013 jones with a low noise current of 0.35pAHz-1/2 under zero bias. A further demonstration of images with high UV to visible light rejection ratio under weak-light illumination of 70nWcm-2 highlights the feasible potential application of low-dimensional perovskite.

First-principles investigation on molecular adsorption on 2D perovskite toward optoelectronic application

Halide perovskite materials have received attention for optoelectronic applications, and it is promising to further engineer the perovskite systems via surface molecular adsorption to improve optoelectronic properties. In this study, we comprehensively investigate atomic structures and properties of surface molecule-modified low-dimensional halide perovskite systems represented by Cs2PbBr4 via first-principles calculations. The calculation pinpoints the effectiveness of molecular adsorption to fine tune the structural and electronic properties of low-dimensional halide perovskite material, which can be stabilized via interfacial secondary bonds such as anion···π, halogen bond and hydrogen bond interactions. Noteworthily, the anion···π interaction is almost ubiquitous in the aromatic molecule/perovskite systems in the present study assuming the adsorption mode is horizontal, signifying the versatility of anion···π interaction to functionalize low-dimensional halide perovskite surfaces. In addition, the amine-containing molecules tend to initiate molecule → perovskite interfacial charge transfer direction upon light excitation while most other organic molecules favors halogen → lead electron transfer process inside the perovskite substrate. Importantly, the polaron calculations suggest the possibility of forming large polarons to protect charge transport via effective electron- and hole-phonon coupling upon molecular adsorption. This study highlights the effectiveness of organic molecule adsorption to fine tune optoelectronic properties of low-dimensional perovskite systems via the formation of interfacial secondary bonds.

Layered Low-Dimensional Ruddlesden-Popper and Dion-Jacobson Perovskites: From Material Properties to Photovoltaic Device Performance.

Layered low-dimensional halide perovskites (LDPs) with multiple quantum well structure have shown increasing research interest in photovoltaic solar cell applications owing to their intrinsic moisture stability and favorable photophysical properties in comparison with their three-dimensional (3D) counterparts. The most common LDPs are Ruddlesden-Popper (RP) phases and Dion-Jacobson (DJ) phases, both of which have made significant research advances in efficiency and stability. However, distinct interlayer cations between RP and DJ phase lead to disparate chemical bonds and different perovskite structures, which endow RP and DJ perovskite with distinctive chemical and physical properties. Plenty of reviews have reported the research progress of LDPs but no summary has elaborated from the perspective of the merits and drawbacks of the RP and DJ phases. Herein, in this review, we offer a comprehensive expound on the merits and promises of RP and DJ LDPs from their chemical structure, physicochemical properties, and photovoltaic performance research progress aiming to provide a new insight into the dominance of RP and DJ phases. Then, we reviewed the recent progress on the synthesis and implementation of RP and DJ LDPs thin films and devices, as well as their optoelectronic properties. Finally, we discussed the possible strategies to resolve existing toughs to realize the desired high-performance LDPs solar cells.

Low Bandgap 2D Perovskite Single Crystal with Anomalous-large Charges/ions Collection Ratio for Ultra-sensitive and Stable X-ray Detectors.

The low-dimensional halide perovskites have attracted increasing attention due to their improved moisture stability, reduced defects, and suppressed ions migration in many optoelectronic devices such as solar cells, light-emitting diodes, X-ray detectors, and so on. However, they are still limited by their large band gap and short charge carriers' diffusion length. Here, we demonstrate that the introduction of metal ions into organic interlayers of two-dimensional (2D) perovskite by cross-linking the copper paddle-wheel cluster-based lead bromide ([Cu(O2 C-(CH2 )3 -NH3 )2 ]PbBr4 ) perovskite single crystals with coordination bonds can not only significantly reduce the perovskite band gap to 0.96 eV to boost the X-ray induced charge carriers, but can also selectively improve the charge carriers' transport along the out-of-plane direction and blocking the ions motion paths. The [Cu(O2 C-(CH2 )3 -NH3 )2 ]PbBr4 single-crystal device can reach a record charges/ions collection ratio of 1.69×1018 ±4.7 % μGyair -1 s, and exhibit a large sensitivity of 1.14×105 ±7% μC Gyair -1 cm-2 with the lowest detectable dose rate of 56 nGyair s-1 under 120 keV X-rays irradiation. In addition, [Cu(O2 C-(CH2 )3 -NH3 )2 ]PbBr4 single-crystal detector exposed to the air without any encapsulation shows excellent X-ray imaging capability with long-term operational stability without any attenuation of 120 days.

Revealing the Mechanism of Pressure-Induced Emission in Layered Silver-Bismuth Double Perovskites.

Pressure-induced emission (PIE) associated with self-trapping excitons (STEs) in low-dimensional halide perovskites has attracted great attention for better materials-by-design. Here, using 2D layered double perovskite (C6 H5 CH2 CH2 NH3 + )4 AgBiBr8 as a model system, we advance a fundamental physicochemical mechanism of the PIE from the perspective of carrier dynamics and excited-state behaviors of local lattice distortion. We observed a pressure-driven STE transformation from dark to bright states, corresponding a strong broadband Stokes-shifted emission. Further theoretical analysis demonstrated that the suppressed lattice distortion and enhanced electronic dimensionality in the excited-state play an important role in the formation of stabilized bright STEs, which could manipulate the self-trapping energy and lattice deformation energy to form an energy barrier between the potential energy curves of ground- and excited-state, and enhance the electron-hole orbital overlap, respectively.

Metal Halide Perovskite Nanowires: Controllable Synthesis, Mechanism, and Application in Optoelectronic Devices.

Metal halide perovskites are promising energy materials because of their high absorption coefficients, long carrier lifetimes, strong photoluminescence, and low cost. Low-dimensional halide perovskites, especially one-dimensional (1D) halide perovskite nanowires (NWs), have become a hot research topic in optoelectronics owing to their excellent optoelectronic properties. Herein, we review the synthetic strategies and mechanisms of halide perovskite NWs in recent years, such as hot injection, vapor phase growth, selfassembly, and solvothermal synthesis. Furthermore, we summarize their applications in optoelectronics, including lasers, photodetectors, and solar cells. Finally, we propose possible perspectives for the development of halide perovskite NWs.

Centimeter-sized Cs3Cu2I5 single crystals grown by oleic acid assisted inverse temperature crystallization strategy and their films for high-quality X-ray imaging

Low-dimensional halide perovskites have become the most promising candidates for X-ray imaging, yet the issues of the poor chemical stability of hybrid halide perovskite, the high poisonousness of lead halides and the relatively low detectivity of the lead-free halide perovskites which seriously restrain its commercialization. Here, we developed a solution inverse temperature crystal growth (ITCG) method to bring-up high quality Cs3Cu2I5 crystals with large size of centimeter order, in which the oleic acid (OA) is introduced as an antioxidative ligand to inhibit the oxidation of cuprous ions effieiently, as well as to decelerate the crystallization rate remarkalby. Based on these fine crystals, the vapor deposition technique is empolyed to prepare high quality Cs3Cu2I5 films for efficient X-ray imaging. Smooth surface morphology, high light yields and short decay time endow the Cs3Cu2I5 films with strong radioluminescence, high resolution (12 lp/mm), low detection limits (53 nGyair/s) and desirable stability. Subsequently, the Cs3Cu2I5 films have been applied to the practical radiography which exhibit superior X-ray imaging performance. Our work provides a paradigm to fabricate nonpoisonous and chemically stable inorganic halide perovskite for X-ray imaging.

Short Aromatic Diammonium Ions Modulate Distortions in 2D Lead Bromide Perovskites for Tunable White-Light Emission

White-light broadband emission in the visible range from the low-dimensional halide perovskites is commonly attributed to structural distortions in lead bromide octahedra. In this paper, we report Dion–Jacobson-phase two-dimensional (2D) lead bromide perovskites based on short aromatic diammonium cations, p-phenylene diammonium (pPDA), m-phenylene diammonium (mPDA), and two 1D compounds templated by o-phenylene diammonium (oPDA). All of the compounds exhibit white-light emission. Single-crystal X-ray diffraction analysis reveals that the distortion of the Pb octahedra is influenced by the stereochemistry of the cations and their interactions with the perovskite layers. Solid-state 1H and 207Pb NMR spectroscopy analysis further confirms this trend, whereby different 1H and 207Pb chemical shifts are observed for the pPDA and mPDA spacer cations, indicating different hydrogen-bonding interactions and octahedral distortions. Owing to the octahedral distortion, 2D (mPDA)PbBr4 compounds exhibit broader white-light emission than 2D (pPDA)PbBr4. Density functional theory calculations suggest that (pPDA)PbBr4 and (mPDA)PbBr4 are direct-band-gap semiconductors, and they exhibit larger electronic band gaps and effective masses than the Ruddlesden–Popper-phase (BA)2PbBr4. Among the films of these compounds, 2D (mPDA)PbBr4 shows the best stability, which is attributed to stronger hydrogen-bonding interactions in the material.

Exploration of sub-bandgap states in 2D halide perovskite single-crystal photodetector

Greater stability of low-dimensional halide perovskites as opposed to their three-dimensional counterparts, alongside their high extinction coefficient and thus excellent emission properties, have made them popular candidates for optoelectronic applications. Topological edges are found in two-dimensional perovskites that show distinct electronic properties. In this work, using Kelvin Probe Force Microscopy, performed on butylammonium lead bromide (BA2PbBr4) single crystals with optical bandgap of ~413 nm, we elucidate the electronic response of the edges and their potential impact on photodetector devices. We show that the charge-carriers are accumulated at the edges, increasing with the edge height. Wavelength-dependent surface photovoltage (SPV) measurements reveal that multiple sub-bandgap states exist in BA2PbBr4. As the edge height increases, the SPV amplitude at the edges reduces slightly more as compared to the adjacent regions, known as terraces, indicating relatively less reduction in band-bending at the surface due possibly to increased de-population of electrons from sub-bandgap states in the upper bandgap half. The existence of sub-bandgap states is further confirmed by the observation of below-bandgap emission (absorption) peaks characterised by spectral photoluminescence and photothermal deflection spectroscopy measurements. Finally, we fabricated a photodetector using a millimetre size BA2PbBr4 single crystal. Noticeable broadband photodetection response was observed in the sub-bandgap regions under green and red illumination, which is attributed to the existence of sub-bandgap states. Our observations suggest edge-height dependence of charge-carrier behaviour in BA2PbBr4 single crystals, a potential pathway that can be exploited for efficient broadband photodetector fabrication.

One-Dimensional Perovskite-like Cu(I)-Halides with Ideal Bandgap Based on Quantum-Well Structure.

Low-dimensional halide perovskites with quantum-well structures are promising materials for electronics and optoelectronics because of their excellent optoelectronic properties. This work concerns two novel, lead-free, one-dimensional organic-inorganic hybrid perovskite-like Cu(I) halides, (MV)Cu2X4 (MV = methyl viologen; X = Br, I), for optoelectronic applications. Both Cu(I) halides exhibited good stability under ambient conditions. The optical bandgaps of (MV)Cu2Br4 and (MV)Cu2I4 are 1.4 and 1.5 eV, respectively, which are in the ideal bandgap range for solar cells. (MV)Cu2Br4 possessed a characteristic quantum-well structure in which [CuBr4]n3n- chains with a nanowire-like structure were rolled up and isolated by tightly packed organic cations. Thanks to quantum confinement in the unique structure, the optical bandgap of (MV)Cu2Br4 fell in the ideal bandgap range for solar cells and was superior to that of (MV)Cu2I4. The good photoresponse properties of these Cu(I) halides suggest their great potential for application as light-harvesting materials in solar cells.

Designing Two-Dimensional Halide Perovskites Based on High-Throughput Calculations and Machine Learning.

The interactions between ions and the low-dimensional halide perovskites are critical to realizing the next-generation energy storage devices such as photorechargeable ion batteries and ion capacitors. In this study, we performed high-throughput calculations and machine-learning analysis for ion adsorption on two-dimensional A2BX4 halide perovskites. The first-principles calculations obtained an initial data set containing adsorption energies of 640 compositionally engineered ion/perovskite systems with diverse ions including Li+, Zn2+, K+, Na+, Al3+, Ca2+, Mg2+, and F-. The machine learning algorithms including k-nearest neighbors (KNN), Kriging, Random Forest, Rpart, SVM, and Xgboost algorithms were compared, and the Xgboost algorithm achieved the best accuracy (r = 0.97, R2 = 0.93) and was selected to predict the virtual design space consisting of 11 976 ion/perovskite systems. The features were then analyzed and ranked according to their Pearson correlations to the output values. In particular, to better understand the features, diverse feature selection methods were employed to comprehensively evaluate the features. The machine-learning-predicted virtual design space was subsequently screened to select stable lead-free ion/perovskite systems with suitable band gaps and halogen mixing features. The present study provides a theoretical foundation to design halide perovskite materials for ion-based energy storage applications such as secondary ion batteries, ion capacitors, and solar-rechargeable batteries.

Atomic resolution in situ observation on photon-induced reshaping and phase transitions of CsPbBr3 nanocube and quantum dot

Controlling the photon-induced reshaping and phase transitions of low-dimensional halide perovskites is a significant and challenging task. Using in situ Cs-corrected transmission electron microscopy with a nanosecond pulsed laser source, we traced CsPbBr3 nanocubes and quantum dots under different laser irradiation conditions, through a low-dose observation mode. We found that a high laser fluence with a short irradiation time (e.g., 300 mJ/cm2 in the range of seconds) triggers defect growth and a cubic-to-orthorhombic phase transition in perovskite nanocubes; however, a low laser fluence with a long irradiation time (e.g., 30 mJ/cm2 in the range of minutes) is actually like an annealing process that removes defects and gradually reshapes the perovskite samples into a round morphology, with the cubic phase well stabilized by the strong surface tension. Based on the in situ studies, we present a feasible and effective laser engineering approach for low-dimensional halide perovskite materials.

Germanium-Based Halide Perovskites: Materials, Properties, and Applications.

Perovskites are attracting an increasing interest in the wide community of photovoltaics, optoelectronic, and detection, traditionally relying on lead-based systems. This Minireview provides an overview of the current status of experimental and computational results available on Ge-containing 3D and low-dimensional halide perovskites. While stability issues analogous to those of tin-based materials are present, some strategies to afford this problem in Ge metal halide perovskites (MHPs) for photovoltaics have already been identified and successfully employed, reaching efficiencies of solar devices greater than 7 % at up to 500 h of illumination. Interestingly, some Ge-containing MHPs showed promising nonlinear optical responses as well as quite broad emissions, which are worthy of further investigation starting from the basic materials chemistry perspective, where a large space for properties modulation through compositions/alloying/fnanostructuring is present.

Perovskite Core-Shell Nanowire Transistors: Interfacial Transfer Doping and Surface Passivation.

While halide perovskite electronics are rapidly developing, they are greatly limited by the inferior charge transport and poor stability. In this work, effective surface charge transfer doping of vapor-liquid-solid (VLS)-grown single-crystalline cesium lead bromide perovskite (CsPbBr3) nanowires (NWs) via molybdenum trioxide (MoO3) surface functionalization is achieved. Once fabricated into NW devices, due to the efficient interfacial charge transfer and reduced impurity scattering, a 15× increase in the field-effect hole mobility (μh) from 1.5 to 23.3 cm2/(V s) is accomplished after depositing the 10 nm thick MoO3 shell. This enhanced mobility is already better than any mobility value reported for perovskite field-effect transistors (FETs) to date. The photodetection performance of these CsPbBr3/MoO3 core-shell NWs is also investigated to yield a superior responsivity (R) up to 2.36 × 103 A/W and an external quantum efficiency (EQE) of over 5.48 × 105% toward the 532 nm regime. Importantly, the MoO3 shell can provide excellent surface passivation to the CsPbBr3 NW core that minimizes the diffusion of detrimental water and oxygen molecules, improving the air stability of CsPbBr3/MoO3 core-shell NW devices. All these findings evidently demonstrate the surface doping as an enabling technology to realize high-mobility and air-stable low-dimensional halide perovskite devices.

Synthesis of halide perovskite microwires via methylammonium cations reaction

Low-dimensional halide perovskites (HPs) have received considerable attention in recent years due to their novel physical properties such as compositional flexibility, high quantum yield, quantum size effects and superior charge transport. Here we show room temperature solution synthesis of 1D organic-inorganic lead bromide perovskite microwires (MWs). Our method uses acetone as a reactant, and when CH3NH3PbBr3 is immersed, acetone reacts with CH3NH3+ cations in the CH3NH3PbBr3 single crystal by the dehydration condensation. The reaction generates a large (CH3)2C = NHCH3+ A-site which cannot be accommodated by the cuboctahedron formed by the corner-sharing [PbBr6]4− octahedral, leading to the transition of corner-sharing octahedra to face-sharing triangular prism and the crystal structure transformation from 3D to 1D. The formation process of (CH3)2C = NHCH3PbBr3 MWs does not involve any ligands, templates or catalysts. A two-terminal memory device was constructed using the (CH3)2C = NHCH3PbBr3 MWs, showing great potential of the method in fabrication of electronic and optoelectronic devices.

High optical nonlinearity in low-dimensional halide perovskite polycrystalline films.

The nonlinear optical properties of low-dimensional polycrystalline halide perovskite films consisting of ethylammonium (EA) and butylammonium (BA) cations are investigated using Z-scan technique. Across the band-edge, two-dimensional (BA)2PbI4 exhibits a transition from saturable absorption (SA) to reverse-SA and its nonlinear absorption and nonlinear refractive index are much smaller than those of bulk counterparts. Meanwhile, EAPbI3 with one-dimensionality of the inorganic structure shows the SA behavior both above and below band-edge and the estimated nonlinear optical parameters of polycrystalline EAPbI3 are comparable to those of single-crystalline ones, attributed to high dielectric contrast between the inorganic and organic elements in one-dimensional structures.