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Two‐dimensional organic–inorganic hybrid perovskites (OIHPs) with alternating structure of the organic and inorganic layers have a natural quantum well structure. The difference of dielectric constants between organic and inorganic layers in this structure results in the enhancement of dielectric confinement effect, which exhibits a large exciton binding energy and hinders the separation of electron‐hole pairs. Herein, a strategy to reduce the dielectric confinement effect by narrowing the dielectric difference between organic amine molecule and [PbBr6]4− octahedron is put forward. The Ethanolamine (EOA) contains hydroxyl groups, resulting in the positive and negative charge centers of O and H non‐overlapping, which generated a larger polarity and dielectric constant. The reduced dielectric constant produces a smaller exciton binding energy (71.03 meV) of (C2H7NO)2PbBr4 ((EOA)2PbBr4) than (C8H11N)2PbBr4 ((PEA)2PbBr4 (156.07 meV), and promotes the dissociation of electrons and holes. The increasing of lifetime of photogenerated carrier in (EOA)2PbBr4 are proved by femtosecond transient absorption spectra. Density functional theory (DFT) calculations have also indicated that the small energy shift of the total density of states (DOS) between the C/H/N and the Pb/Br in (EOA)2PbBr4 favors the separation of electrons and holes. In addition, this work demonstrates the application of (PEA)2PbBr4 and (EOA)2PbBr4 in the field of photocatalytic CO2 reduction. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid perovskites like methylammonium lead iodide (MAPbI3) have received extensive attention in solar energy conversion due to their superb optoelectronic properties. However, the serious charge recombination at the nanoscale domain and the lack of catalytic sites on the perovskite's surface seriously limit their photocatalytic hydrogen evolution activities. Taking MAPbI3 as a typical example, we show that coupling amorphous molybdenum phosphide (MoP) cocatalyst with MAPbI3 can significantly enhance the photocatalytic H2 evolution performance of MAPbI3. The MoP coupling can accelerate the electron extraction from MAPbI3 and promote the hydrogen evolution reaction catalysis. Consequently, the photocatalytic hydrogen evolution activity of MoP/MAPbI3 is ca. 97 times higher than that of bare MAPbI3. Moreover, the MoP/MAPbI3 exhibits good stability during cycling tests. This work demonstrates the possibility of employing amorphous MoP as a non-noble metal-based cocatalyst in a hybrid perovskite-based photocatalytic hydrogen production reaction. Methylammonium lead iodide (MAPbI3) loaded with molybdenum phosphide (MoP) cocatalyst demonstrates 97 times higher photocatalytic hydrogen evolution activity than bare MAPbI3 from HI splitting reaction under visible light irradiation. [ABSTRACT FROM AUTHOR]

As an important photovoltaic material, organic–inorganic hybrid perovskites have attracted much attention in the field of solar cells, but their instability is one of the main challenges limiting their commercial application. However, the search for stable perovskites among the thousands of perovskite materials still faces great challenges. In this work, the energy above the convex hull values of organic–inorganic hybrid perovskites was predicted based on four different machine learning algorithms, namely random forest regression (RFR), support vector machine regression (SVR), XGBoost regression, and LightGBM regression, to study the thermodynamic phase stability of organic–inorganic hybrid perovskites. The results show that the LightGBM algorithm has a low prediction error and can effectively capture the key features related to the thermodynamic phase stability of organic–inorganic hybrid perovskites. Meanwhile, the Shapley Additive Explanation (SHAP) method was used to analyze the prediction results based on the LightGBM algorithm. The third ionization energy of the B element is the most critical feature related to the thermodynamic phase stability, and the second key feature is the electron affinity of ions at the X site, which are significantly negatively correlated with the predicted values of energy above the convex hull (Ehull). In the screening of organic–inorganic perovskites with high stability, the third ionization energy of the B element and the electron affinity of ions at the X site is a worthy priority. The results of this study can help us to understand the correlation between the thermodynamic phase stability of organic–inorganic hybrid perovskites and the key features, which can assist with the rapid discovery of highly stable perovskite materials. [ABSTRACT FROM AUTHOR]

Organic-inorganic methylammonium lead iodide perovskite (MAPbI3) nanowires (NWs) have attracted significant attention in the realm of optoelectronic devices due to their outstanding optoelectronic properties. However, the persistent challenge of high trap densities has been a limiting factor in realizing their full potential in device performance. To address this challenge, we incorporated cesium (Cs) and systematically investigated the impact of Cs concentration on the trap densities and the optoelectronic characteristics of Cs x MA(1− x)PbI3 NWs. Our findings unveiled an initial reduction in trap densities as Cs+ content increased, with the lowest point occurring at x = 0.2. However, beyond this threshold, trap densities began to rise, eventually surpassing those observed in pure MAPbI3 at x = 0.4. Furthermore, we fabricated single NW photodetectors to assess how Cs+ content influenced optoelectronic properties. The results indicated that Cs+ incorporation led to enhancements in photocurrent and response speed, withthe optimal performance observed at x = 0.2. Our study provides valuable insights into the role of Cs+ incorporation in tailoring the optoelectronic properties of perovskite NWs. [ABSTRACT FROM AUTHOR]

The importance of the phonon bottleneck effect on the optoelectronic properties of organic-inorganic hybrid perovskites (OIHPs) has been well documented. While randomly distributed multiple quantum wells (MQWs) are frequently generated in 2D/3D perovskite heterostructures, the influence of MQWs formation in 2D/3D perovskite heterostructures on the phonon bottleneck effect is poorly understood. In this study, we construct 2D/3D perovskite heterostructures using 2D OIHP (NH3(CH2)8NH3PbI4, OdAPbI4) to passivate 3D OIHP (FAPbI3) and investigate their excitons and carrier dynamics by employing photoluminescence (PL) spectroscopy and femtosecond optical-pump terahertz-probe spectroscopy (fsOPTPS). We observe the formation of MQWs and establish a structure-dynamics-property relationship among the exciton formation time (TEF), the hot carrier cooling rate (kcool) and the effective charge-carrier mobility(ϕμ). The formation of MQWs could significantly invalidate the phonon bottleneck effect and modulate the optoelectronic properties of 2D/3D perovskite heterostructures. This work provides valuable information on the importance of band alignment and the phonon bottleneck effect in the strategy of 2D/3D perovskite heterostructures. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) organic–inorganic hybrid perovskites (OIHPs) have drawn increased attention due to rich physical properties such as ferroelectricity and photovoltaic properties. Nevertheless, it is challenging to discover novel 2D OIHPs within the vast chemical composition space. Herein, a diagrammatic machine learning model was employed to improve this issue. We collected 179 OIHPs with a variety of organic cations and screened out 6 features from 10,622 descriptors. Subsequently, a decision tree model was created to predict the dimensionality of OIHPs, achieving a LOOCV accuracy of 0.94 and a test accuracy of 0.89, respectively. Then, one candidate from a virtual space with 8256 samples was successfully synthesized, which was consistent with the prediction of the model. Finally, three rules were produced by visualization of the tree structure to generally discriminate 2D from non-2D OIHPs. It is believed that the diagrammatic model has reliability in identifying 2D OIHPs and will serve further property studies of OIHPs in the future.

Organic‐inorganic hybrid perovskite (MAPbX3) is known having excellent photoelectric properties. Compared to polycrystalline films, perovskite micro/nanowires can provide improved optoelectronic properties, mechanical flexibility, and adaptability due to higher crystallinity. However, their economical, scalable, and controllable fabrication remains a challenge. In this work, the authors report a facile way to fabricate high‐quality MAPbX3 triangular‐micro‐wires (TMWs). The Si/SiO2 substrate with triangular‐micro‐trenches (TMTs) array serves as the template for the growth of MAPbX3 TMWs array through blade coating. The MAPbX3 TMW first nucleated at the trench bottom, which facilitating the nanowire growth with high crystallinity. In addition, the size and periodicity of TMTs array can be independently controlled, providing potential for scale‐up device applications. The photodetectors fabricated with these MAPbI3 TMWs show excellent responsivity of (144.5 ± 2.1) A/W and specific detectivity of (2.7 ± 0.02) × 1011 Jones under weak light (0.5 µW cm−2). Their photoresponse to pulsed light is stable and reproducible, with rise and decay times of 7.5 and 6.0 ms, respectively. Finally, with the demonstration of the image sensor application, MAPbX3 TMWs array is anticipated to be suitable for large‐area, high‐performance integrated optoelectronics. [ABSTRACT FROM AUTHOR]

The design and fabrication of a flexible electric‐optical perovskite/electrolyte synaptic transistor are demonstrated for the first time, which emulates important neuromorphic functions under dual‐mode modulation. Benefiting from the bipolar charge transport properties of light‐harvesting perovskite and the high specific capacitance and mechanically robust multi‐ion electrolyte, the device exhibits bidirectional plasticity, better reliability, retaining >70% of the initial current level after 2500 flex per flat laps, and a very wide operating voltage window from 0.04 to 10 V, and responsive to ultralow stimuli down to tens of millivolt level with femtojoule‐level energy consumption. The synergistic high response under dual‐mode modulation enables the device to emulate complex neural learning rules and achieve neuromorphic applications, including classical conditioning and spatiotemporal learning, and image recognition tasks with higher accuracy of 81%. Moreover, an enhanced artificial reflex‐arc behavior is emulated by employing the flexible electro‐optical artificial synapses that serve as key information‐receiving‐processing units to manipulate the actions of electrochemical artificial muscles to a larger extent. These properties show great potential in soft neurorobotic systems and prostheses. [ABSTRACT FROM AUTHOR]

Cl, Br, and I are elements in the halogen family, and are often used as dopants in semiconductors. When employed as dopants, these halogens can significantly modify the optoelectronic properties of materials. From the perspective of halogen doping, we have successfully achieved the stabilization of crystal structures in CH3NH3PbX3, CH3NH3PbI3−xClx, CH3NH3PbI3−xBrx, and CH3NH3PbBr3−xClx, which are organic–inorganic hybrid perovskites. Utilizing first-principles density functional theory calculations with the CASTEP module, we investigated the optoelectronic properties of these structures by simulations. According to the calculations, a smaller difference in electronegativity between different halogens in doped structures can result in smoother energy bands, especially in CH3NH3PbI3−xBrx and CH3NH3PbBr3−xClx. The PDOS of the Cl-3p orbitals undergoes a shift along the energy axis as a result of variances in electronegativity levels. The optoelectronic performance, carrier mobility, and structural stability of the CH3NH3PbBr3−xClx system are superior to other systems like CH3NH3PbX3. Among many materials considered, CH3NH3PbBr2Cl exhibits higher carrier mobility and a relatively narrower bandgap, making it a more suitable material for the absorption layer in solar cells. This study provides valuable insights into the methodology employed for the selection of specific types, quantities, and positions of halogens for further research on halogen doping. [ABSTRACT FROM AUTHOR]

Transmission electron microscope (TEM) is thought as one powerful tool to imaging the atomic-level structure of organic inorganic hybrid perovskite (OIHP) materials, which provides valuable and essential guidance toward high performance OIHP-related devices. However, these OIHPs exhibit poor electron beam stability, severely limiting their practical applications in TEM. Here in this article, the application of TEM to obtain atomic-scale image of OIHPs, main obstacles in identifying the degradation product and future prospects of TEM in the characterization of OIHP materials are reviewed and presented. Three potential strategies (sample protection, low temperature technology, and low-dose technologies) are also proposed to overcome the current drawback of TEM technology. [ABSTRACT FROM AUTHOR]

We have synthesised and characterised 21 new ternary Pb(II) bromides with 16 different pyridine‐based organic cations by single crystal XRD measurements. The dominating composition is APbBr3 with 10 representatives, but also 6 examples for APb2Br5 were found. The systematic variation of topological aspects of the organic cations allowed conclusions on the influence of N−H⋅⋅⋅Br hydrogen bridges on the connectivity and bonding situation of the Pb−Br polyhedra. Additionally, it turned out, that further weak ionic interactions can have an influence, if the formation of N−H⋅⋅⋅Br hydrogen bridges is hindered by steric effects. In general, the high versatility of the dominating PbBr6 octahedra, and in some cases higher or lower coordination numbers, allows conclusions on the parameters that influence pattern and extent of the N−H⋅⋅⋅Br bridges as the strongest structure‐determining factor. Type and extent of N−H⋅⋅⋅Br bridges have also an impact on the distortion of the PbBr6 octahedra ranging from nearly regular PbBr6 octahedra to 2+2+2 and 1+2+2+1 patterns with significant lone pair activity. Finally, the connectivity mode of the octahedra relates to formation and strength of hydrogen bonds. [ABSTRACT FROM AUTHOR]

We have synthesised and characterised 21 new ternary Pb(II) bromides with 16 different pyridine‐based organic cations by single crystal XRD measurements. The dominating composition is APbBr3 with 10 representatives, but also 6 examples for APb2Br5 were found. The systematic variation of topological aspects of the organic cations allowed conclusions on the influence of N−H⋅⋅⋅Br hydrogen bridges on the connectivity and bonding situation of the Pb−Br polyhedra. Additionally, it turned out, that further weak ionic interactions can have an influence, if the formation of N−H⋅⋅⋅Br hydrogen bridges is hindered by steric effects. In general, the high versatility of the dominating PbBr6 octahedra, and in some cases higher or lower coordination numbers, allows conclusions on the parameters that influence pattern and extent of the N−H⋅⋅⋅Br bridges as the strongest structure‐determining factor. Type and extent of N−H⋅⋅⋅Br bridges have also an impact on the distortion of the PbBr6 octahedra ranging from nearly regular PbBr6 octahedra to 2+2+2 and 1+2+2+1 patterns with significant lone pair activity. Finally, the connectivity mode of the octahedra relates to formation and strength of hydrogen bonds. [ABSTRACT FROM AUTHOR]

Recently organic–inorganic hybrid perovskite (OIHP) has risen suddenly to become a superstar for spintronic applications. Fundamental understanding of its spin properties is of great importance for future advances of its applications in spin‐optoelectronic devices. In this work, the authors pioneer modulation of the spin Seebeck thermopower (SSTP) in a Pt/MAPbBr3/NiFe nonlocal structure via longitudinal spin Seebeck effect measurements. They unravel the effective magnon injection into the perovskite film from the NiFe layer, and the tunability of SSTP in this structure is easily realized through the optimization of morphology and component engineering of the OIHP film. First, upon biasing samples with a magnetic flux density during the preparation process, a high‐quality OIHP film can be obtained, in which the spin scattering can be reduced leading to the SSTP enhancement. Second, by doping Cr into the OIHP lattice, the increased magnetic moment density and the additional in‐plane inverse Rashba–Edelstein effect synergistically improve spin accumulation in the Pt layer and thus tune its SSTP. Unveiling those phenomena is important to understanding magnon transport in the OIHP interlayer, which is instructive for designing magnonic devices based on OIHP film. [ABSTRACT FROM AUTHOR]

Cl, Br, and I are elements in the halogen family, and are often used as dopants in semiconductors. When employed as dopants, these halogens can significantly modify the optoelectronic properties of materials. From the perspective of halogen doping, we have successfully achieved the stabilization of crystal structures in CH3NH3PbX3, CH3NH3PbI3−xClx, CH3NH3PbI3−xBrx, and CH3NH3PbBr3−xClx, which are organic–inorganic hybrid perovskites. Utilizing first-principles density functional theory calculations with the CASTEP module, we investigated the optoelectronic properties of these structures by simulations. According to the calculations, a smaller difference in electronegativity between different halogens in doped structures can result in smoother energy bands, especially in CH3NH3PbI3−xBrx and CH3NH3PbBr3−xClx. The PDOS of the Cl-3p orbitals undergoes a shift along the energy axis as a result of variances in electronegativity levels. The optoelectronic performance, carrier mobility, and structural stability of the CH3NH3PbBr3−xClx system are superior to other systems like CH3NH3PbX3. Among many materials considered, CH3NH3PbBr2Cl exhibits higher carrier mobility and a relatively narrower bandgap, making it a more suitable material for the absorption layer in solar cells. This study provides valuable insights into the methodology employed for the selection of specific types, quantities, and positions of halogens for further research on halogen doping.

Transmission electron microscope (TEM) is thought as one powerful tool to imaging the atomic-level structure of organic inorganic hybrid perovskite (OIHP) materials, which provides valuable and essential guidance toward high performance OIHP-related devices. However, these OIHPs exhibit poor electron beam stability, severely limiting their practical applications in TEM. Here in this article, the application of TEM to obtain atomic-scale image of OIHPs, main obstacles in identifying the degradation product and future prospects of TEM in the characterization of OIHP materials are reviewed and presented. Three potential strategies (sample protection, low temperature technology, and low-dose technologies) are also proposed to overcome the current drawback of TEM technology.

Micro/nano optoelectronic devices based on curved substrates play a significant role in the development of wearable devices, electronic skin, conformal sensors, conformal antennas, and soft robots. However, the current fabrication processes are oriented toward planar micro/nano devices, and the fabrication of such devices on curved substrates is challenging. Herein, a temperature‐gradient‐assisted nanoimprint‐based in situ micro/nano‐crystal growth method is proposed to fabricate high‐quality curved perovskite microwire crystal (MWC) arrays on curved surfaces. Based on this curved perovskite MWC array without bending‐induced defects, high‐performance curved photodetectors (responsivity = 414 A W−1, detectivity = 1.2 × 1014 Jones, and external quantum efficiency over 140 000%) with extraordinary stability (85% of original performance maintained for more than 2 years) are fabricated to realize a curved imaging device. These results provide insights into the application of high‐performance perovskite photodetectors in nonconformal optical systems. [ABSTRACT FROM AUTHOR]

The poor stability of organic–inorganic hybrid perovskites hinders its commercial application, which motivates a need for greater theoretical insight into its binding mechanism. To date, the binding mode of organic cation and anion inside organic–inorganic hybrid perovskites is still unclear and even contradictory. Therefore, in this work based on density functional theory (DFT), the binding mechanism between organic cation and anion was systematically investigated through electronic structure analysis including an examination of the electronic localization function (ELF), electron density difference (EDD), reduced density gradient (RDG), and energy decomposition analysis (EDA). The binding strength is mainly determined by Coulomb effect and orbital polarization. Based on the above analysis, a novel 2D linear regression descriptor that Eb = − 9.75Q2/R0 + 0.00053 V∙EHL − 6.11 with coefficient of determination R2 = 0.88 was proposed to evaluate the binding strength (the units for Q, R0, V, and EHL are |e|, Å, bohr3, and eV, respectively), revealing that larger Coulomb effect (Q2/R0), smaller volume of perovskite (V), and narrower energy difference (EHL) between the lowest unoccupied molecular orbital (LUMO) of organic cation and the highest occupied molecular orbital (HOMO) of anion correspond to the stronger binding strength, which guides the design of highly stable organic–inorganic hybrid perovskites. [ABSTRACT FROM AUTHOR]

As an important photovoltaic material, organic-inorganic hybrid perovskites have attracted much attention in the field of solar cells, but their instability is one of the main challenges limiting their commercial application. However, the search for stable perovskites among the thousands of perovskite materials still faces great challenges. In this work, the energy above the convex hull values of organic-inorganic hybrid perovskites was predicted based on four different machine learning algorithms, namely random forest regression (RFR), support vector machine regression (SVR), XGBoost regression, and LightGBM regression, to study the thermodynamic phase stability of organic-inorganic hybrid perovskites. The results show that the LightGBM algorithm has a low prediction error and can effectively capture the key features related to the thermodynamic phase stability of organic-inorganic hybrid perovskites. Meanwhile, the Shapley Additive Explanation (SHAP) method was used to analyze the prediction results based on the LightGBM algorithm. The third ionization energy of the B element is the most critical feature related to the thermodynamic phase stability, and the second key feature is the electron affinity of ions at the X site, which are significantly negatively correlated with the predicted values of energy above the convex hull (E hull ). In the screening of organic-inorganic perovskites with high stability, the third ionization energy of the B element and the electron affinity of ions at the X site is a worthy priority. The results of this study can help us to understand the correlation between the thermodynamic phase stability of organic-inorganic hybrid perovskites and the key features, which can assist with the rapid discovery of highly stable perovskite materials.

SnO2 has been universally applied as electron transporting layer (ETL) towards the fabrication of highly efficient perovskite solar cells (PSCs), owing to its unique advantages including low‐temperature solution‐processability, high optical, transmittance and good electrical conductivity. Uncoordinated Sn‐dangling bonds on SnO2 surface exist as deep traps to capture the photogenerated carriers, causing hysteresis and device instability. Fullerene derivatives, though being widely utilized as the passivator for SnO2, are highly prone to self‐aggregate due to their π‐cage structures, which hampers passivation. Herein, π‐conjugated n‐type small molecules with better film formation ability are innovatively designed, to improve passivation effectiveness. By exploring the interplay between molecular stacking of small molecules and charge transporting/recombination dynamics at the SnO2/perovskite interface, it is unveiled that a more compact molecular packing of the organic passivators yields superior interfacial characteristics, in terms of fewer trap states, lower charge recombination and higher electron transporting efficiency. An impressive PCE over 23% is achieved with the assistance of this new‐type SnO2‐passivator, which is among the highest reported value for triple‐cation perovskite systems to date. This work offers an original concept for the design and synthesis of ETL passivators towards the development of high performance and stable PSCs. [ABSTRACT FROM AUTHOR]

Electroluminescence efficiency and operating stability of solution‐processed perovskite light‐emitting diodes (PeLEDs) are limited by luminescence quenching induced by indium or tin released from indium tin oxide (ITO) electrode upon deposition of highly acidic conventional hole injection layer (HIL) (i.e., poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)) and inefficient hole injection into perovskite emitting layer. Here, a synergistic molecular strategy to develop a neutralized gradient HIL, which possesses low acidity and high work function (WF) simultaneously, is proposed. First, it is shown that aniline with relatively low basicity and dipole moment efficiently neutralizes HIL while maintaining its original confirmation and high WF. Both acidity‐neutralizing aniline and WF‐modifying agent (perfluorinated ionomer) are incorporated into PEDOT:PSS to achieve high pH ≈ 6 and WF > 5.8 eV, which suppresses etching of underlying ITO and luminescence quenching while maintaining efficient hole injection into perovskite emitting layer. With this synergetic molecular engineering, high current efficiency = 52.55 cd A−1 with extended operating lifetime is achieved in PeLEDs that use colloidal formamidinium lead bromide nanoparticle films. This result provides a simple and efficient way to develop efficient and stable PeLEDs in industrial displays and solid‐state lighting. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid perovskites such as methylammonium lead iodide (MAPbI3) materials have recently attracted great attention due to their potential for photovoltaic applications. The performance and stability of these perovskite solar cells are sensitive to water and moisture in an ambient environment. Thus, an understanding of how water influences MAPbI3 and particularly the role of grain boundary (GB) defects is important for developing appropriate mitigation strategies. Herein, water molecular diffusion in ∑5‐(210) GB is investigated and compared with pristine MAPbI3 using first‐principles calculations. Water diffusion along the ∑5‐(210) GB is found to be facile with a 0.07 eV energy barrier while diffusion barrier from GB core to bulk is 0.24 eV. In contrast, the diffusion process in bulk MAPbI3 is relatively large 0.70 eV due to water interactions with the Pb–I network. Further, it is shown that water is more stable in the GB region compared with the pristine system. Thus, the strong thermodynamic and kinetic tendencies for water segregation to the GBs in MAPbI3 suggests that improving the crystallinity of MAPbI3 is an effective strategy to slow down water degradation processes in agreement with recent experimental results.

Organic–inorganic halide perovskite (OIHP) solar cells have garnered great attention in the last decade since they continuously approach the Shockley–Queisser Limit. Compared with conventional organic and inorganic semiconductors, OIHPs possess the high tolerance on defects due to the dominated intrinsically shallow‐level carrier‐trapping centers. However, the existence of defects still causes the ion migration, produces the hysteresis effect, and accelerates the film degradation, eventually suppressing the device efficiency and stability. In this Review Article, we summarize recent impressive advance on passivating OIHP defects and discuss the future horizon of exploiting high‐efficiency and long‐stability OIHP solar cells in terms of defect managements. [ABSTRACT FROM AUTHOR]

Inspired by the low energy consumption, high parallel and fault‐tolerance of visual perception system in human brain, optoelectronic devices integrated with the sensing, memory, and signal processing functionalities become the candidate to emulate functions of photonic synapse. Herein, red‐light‐stimulated nonvolatile perovskite‐based photomemory through optimized thickness of poly(3‐hexylthiophene‐2,5‐diyl)(P3HT) is demonstrated. The device emulates important synaptic functions which can be manipulated by light intensity, light pulse interval, and number of presynaptic spikes. The lower photon energy triggered photonic device paves the way for developing low energy consumption of neuromorphic computing in the future.

Spinterfaces are due to the orbital hybridization at an interface of a ferromagnet and a nonmagnetic semiconductor. Interfacial densities of states (i‐DOS) are spin‐dependent, which may offer the spin‐filter effect for enhancing spin‐polarized charge injection efficiency and magnetic field effects (MFEs). In the work, a prototypical perovskite spin valve (PeSV) comprising Ni/MAPbI3−xClx/Ni (MA = CH3NH3) is fabricated, showing a clear magnetic switching behavior in the ambient condition. It is further explored by studying the magnetophotocurrent (MPC) at the short‐circuit current density condition (magneto‐Jsc). Anomalously large magneto‐Jsc can be detected by comparing to devices with nonmagnetic Au electrodes. The effect can be more pronounced for the quasi‐2D perovskite such as (PEA)2(MA)3Pb4I13 (PEA = C6H5(CH2)2NH3). At low fields, the hyperfine field induced spin‐mixing shows remarkable magneto‐Jsc signals for it. In addition, the circularly and linearly polarized laser beam can effectively manipulate the magnitude of magneto‐Jsc for both MAPbI3−xClx and (PEA)2(MA)3Pb4I13. It is postulated that the formation of the spinterfaces may play a dominant role for the large and tunable magneto‐Jsc effect. These studies may pave the way for future experimental and theoretical studies in the field. [ABSTRACT FROM AUTHOR]

The explosive growth of the information era has put forward urgent requirements for ultrahigh-speed and extremely efficient computations. In direct contrary to charge-based computations, spintronics aims to use spins as information carriers for data storage, transmission, and decoding, to help fully realize electronic device miniaturization and high integration for next-generation computing technologies. Currently, many novel spintronic materials have been developed with unique properties and multifunctionalities, including organic semiconductors (OSCs), organic-inorganic hybrid perovskites (OIHPs), and 2D materials (2DMs). These materials are useful to fulfill the demand for developing diverse and advanced spintronic devices. Herein, these promising materials are systematically reviewed for advanced spintronic applications. Due to the distinct chemical and physical structures of OSCs, OIHPs, and 2DMs, their spintronic properties (spin transport and spin manipulation) are discussed separately. In addition, some multifunctionalities due to photoelectric and chiral-induced spin selectivity (CISS) are overviewed, including the spin-filter effect, spin-photovoltaics, spin-light emitting devices, and spin-transistor functions. Subsequently, challenges and future perspectives of using these multifunctional materials for the development of advanced spintronics are presented., (© 2023 Wiley‐VCH GmbH.)

Switchable spontaneous polarization is the vital property of ferroelectrics, which leads to other key physical properties such as piezoelectricity, pyroelectricity, and nonlinear optical effects, etc. Recently, organic-inorganic hybrid perovskites with 2D layered structure have become an emerging branch of ferroelectric materials. However, most of the 2D hybrid ferroelectrics own relatively low polarizations (<15 µC cm -2 ). Here, a strategy to enhance the polarization of these hybrid perovskites by using ortho-, meta-, para-halogen substitution is developed. Based on (benzylammonium) 2 PbCl 4 (BZACL), the para-chlorine substituted (4-chlorobenzylammonium) 2 PbCl 4 (4-CBZACL) ferroelectric semiconductor shows a large spontaneous polarization (23.3 µC cm -2 ), which is 79% larger than the polarization of BZACL. This large enhancement of polarization is successfully explained via ab initio calculations. The study provides a convenient and efficient strategy to promote the ferroelectric property in the hybrid perovskite family., (© 2023 Wiley-VCH GmbH.)

In this work, methylammonium lead tribromide (MAPbBr3) single crystals are studied by noncontact atomic force microscopy (nc-AFM) and Kelvin probe force microscopy (KPFM). We demonstrate that the surface photovoltage and crystal photostriction can be simultaneously investigated by implementing a specific protocol based on the acquisition of the tip height and surface potential during illumination sequences. The obtained data confirm the existence of lattice expansion under illumination in MAPbBr3 and that negative photocarriers accumulate near the crystal surface due to band bending effects. Time-dependent changes of the surface potential occurring under illumination on the scale of a few seconds reveal the existence of slow ion-migration mechanisms. Lastly, photopotential decay at the sub-millisecond time scale related to the photocarrier lifetime is quantified by performing KPFM measurements under frequency-modulated illumination. Our multimodal approach provides a unique way to investigate the interplay between the charges and ionic species, the photocarrier-lattice coupling and the photocarrier dynamics in hybrid perovskites.

This paper reports a comparative study of thermal stability between all-organic metal halide perovskite (MHP) CsPbBr3 and organic–inorganic hybrid MHP (methylammonium lead bromide MAPbBr3). The film morphology, crystal structure, steady-state photoluminescence intensity, and photoluminescence lifetime of CsPbBr3 and MAPbBr3 polycrystalline films were measured after thermal annealing at temperatures from 70°C to 230°C. The CsPbBr3 films exhibited little change in their structural and luminescent properties after being annealed even at 230°C, whereas the MAPbBr3 films exhibited a significant change in such properties due to their decomposition into PbBr2 when annealed at ≥180°C. This study increased the understanding of the difference in the thermal stability of MHP polycrystalline films with different A-site cations.

In the last decade, hybrid materials have received widespread attention. In particular, hybrid lead halide perovskite‐type semiconductors are very attractive owing to their great flexibility in band gap engineering. Here, by using precise molecular modifications, three one‐dimensional perovskite‐type semiconductor materials are designed and obtained: [Me3PCH2X][PbBr3] (X=H, F, and Cl for compounds 1, 2, and 3, respectively). The introduction of a heavier halogen atom (F or Cl) to [Me4P]+ increases the potential energy barrier required for the tumbling motion of the cation, hence achieving the transformation of the phase transition temperature from low temperature (192 K) to room temperature (285 K) and high temperature (402.3 K). Moreover, the optical band gaps reveal a broadening trend with 3.176 eV, 3.215 eV, and 3.376 eV along the H→F→Cl series, which is attributed to the formation of the structural distortion. [ABSTRACT FROM AUTHOR]

By using low-dose electron diffraction and imaging techniques, the structural instabilities of organic–inorganic hybrid perovskites (OIHPs) have been systematically investigated with controlled exposure facet, temperature and accelerating voltage to reveal the optimized conditions for TEM characterizations of OIHPs, which guides the successful acquisition of the atomic structure of CH 3 NH 3 PbI 3. Organic-inorganic hybrid perovskites (OIHPs) have attracted extensive research interest as a promising candidate for efficient and inexpensive solar cells. Transmission electron microscopy (TEM) characterizations that can benefit the fundamental understanding and the degradation mechanism are widely used for these materials. However, their sensitivity to the electron beam illumination and hence structural instabilities usually prevent us from obtaining the intrinsic information or even lead to significant artifacts. Here, we systematically investigate the structural degradation behaviors under different experimental factors to reveal the optimized conditions for TEM characterizations of OIHPs by using low-dose electron diffraction and imaging techniques. We find that a low temperature (−180 °C) does not slow down the beam damage but instead induces a rapid amorphization for OIHPs. Moreover, a less severe damage is observed at a higher accelerating voltage. The beam-sensitivity is found to be facet-dependent that a (1 0 0) exposed CH 3 NH 3 PbI 3 (MAPbI 3) surface is more stable than a (0 0 1) surface. With these guidance, we successfully acquire the atomic structure of pristine MAPbI 3 and identify the characterization window that is very narrow. These findings are helpful to guide future electron microscopy characterizations of these beam-sensitive materials, which are also useful for finding strategies to improve the stability and performance of the perovskite solar cells. [ABSTRACT FROM AUTHOR]

Perovskite‐based photomemory adopting a floating‐gate architecture recently attracts research attention for developing efficient photo‐recording devices due to its simplified structure and non‐contact light‐programming feature. Herein, the memory characteristics of such type device is improved by the precise control of the size of perovskite nanocrystals (NCs) in the hybrid floating gate. Compared to the previous case of using polystyrene (PS) as the host polymer matrix, a N‐containing polymer, poly(2‐vinyl pyridine) (P2VP), is revealed to better regulate the size of embedded perovskite NCs into the nanometer level (7–9 nm) owing to the intense coordination between the N atom in P2VP and the Pb2+ ions of perovskite through Lewis acid‐base interaction. As benefitting from the reduced current dissipation and interfacial charge recombination at the gate/channel interface, the P2VP‐derived photomemory not only delivers a much higher On/Off current ratio (105) than the value (103) of the reference PS‐based device but also requires a much shorter illumination time (5 s) and low drain voltage (‐1 V) to achieve decent photo‐recording function. Besides, it possesses good long‐term retention for 104 s, excellent stress endurance over 100 cycles, and respectable ambient stability over 6 months due to the well isolation of perovskite NCs in the P2VP matrix. [ABSTRACT FROM AUTHOR]

Quasi‐2D metal halide perovskite films are promising for efficient light‐emitting diodes (LEDs), because of their efficient radiative recombination and suppressed trap‐assisted quenching compared with pure 3D perovskites. However, because of the multidomain polycrystalline nature of solution‐processed quasi‐2D perovskite films, the composition engineering always impacts the emitting properties with complicated mechanisms. Here, defect passivation and domain distribution of quasi‐2D perovskite films prepared with various precursor compositions are systematically studied. As a result, in perovskite films prepared from stoichiometric quasi‐2D precursor compositions, large organic ammonium cations function well as passivators. In comparison, precursor compositions of simply adding large organic halide salt into a 3D perovskite precursor ensure not only the defect passivation but also the effective formation of quasi‐2D perovskite domains, avoiding unfavorable appearance of low‐order domains. Quasi‐2D perovskite films fabricated with a well‐designed precursor composition achieve a high photoluminescence quantum yield of 95.3% and an external quantum efficiency of 14.7% in LEDs. [ABSTRACT FROM AUTHOR]

Micro‐ring resonators are widely used in many fields due to their compact structure, high integration, and rich functions. In recent years, perovskite materials have been widely concerned because of their superior properties and various shapes of perovskite‐based optical resonators have been achieved. Despite the excellent photoelectric properties of perovskite materials, it is difficult to realize micro‐ring resonators based on perovskite materials due to its tendency to crystallize into cubic structures. Here, this problem is solved by a microstructure edge‐guided crystallization method to fabricate shape‐designable and size‐tunable methylammonium lead bromide (MAPbBr3) micro‐ring resonator arrays with high performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two-dimensional organic–inorganic hybrid perovskites were identified based on our diagrammatic machine learning model with an accuracy of > 90 %. • A two-dimensional perovskite candidate designed from a visual pattern recognition projection was successfully synthesized. • Three rules for guiding the formation of two-dimensional organic–inorganic hybrid perovskites were extracted from the decision tree model. Two-dimensional (2D) organic–inorganic hybrid perovskites (OIHPs) have drawn increased attention due to rich physical properties such as ferroelectricity and photovoltaic properties. Nevertheless, it is challenging to discover novel 2D OIHPs within the vast chemical composition space. Herein, a diagrammatic machine learning model was employed to improve this issue. We collected 179 OIHPs with a variety of organic cations and screened out 6 features from 10,622 descriptors. Subsequently, a decision tree model was created to predict the dimensionality of OIHPs, achieving a LOOCV accuracy of 0.94 and a test accuracy of 0.89, respectively. Then, one candidate from a virtual space with 8256 samples was successfully synthesized, which was consistent with the prediction of the model. Finally, three rules were produced by visualization of the tree structure to generally discriminate 2D from non-2D OIHPs. It is believed that the diagrammatic model has reliability in identifying 2D OIHPs and will serve further property studies of OIHPs in the future. [ABSTRACT FROM AUTHOR]

Methylammonium lead halide perovskite‐based solar cells have demonstrated efficiencies as high as 24.2 %, highlighting their potential as inexpensive and solution‐processable alternatives to silicon solar cell technologies. Poor stability towards moisture, ultraviolet irradiation, heat, and a bias voltage of the perovskite layer and its various device interfaces limits the commercial feasibility of this material for outdoor applications. Herein, we investigate the role of hydrogen bonding interactions induced when metal halide perovskite crystals are crosslinked with alkyl or π‐conjugated boronic acid small molecules (‐B(OH)2). The crosslinked perovskite crystals are investigated under continuous light irradiation and moisture exposure. These studies demonstrate that the origin of the interaction between the alkyl or π‐conjugated crosslinking molecules is due to hydrogen bonding between the ‐B(OH)2 terminal group of the crosslinker and the I of the [PbI6]4− octahedra of the perovskite layer. Also, this interaction influences the stability of the perovskite layer towards moisture and ultraviolet light irradiation. Morphology and structural analyses, as well as IR studies as a function of aging under both dark and light conditions show that π‐conjugated boronic acid molecules are more effective crosslinkers of the perovskite crystals than their alkyl counterparts thus imparting better stability towards light and moisture degradation. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid perovskites, which attract tremendous attention due to their incredible rise in power conversion efficiencies of new-generation solar cells, have proved to be promising semiconductor materials for photoelectric devices. However, the research of this kind of perovskites as electric memory materials is rarely reported. We herein report a series of new perovskites (CH 3 NH 3 MBr 3 , where "M" refers to Pb2+ or the mixed Pb2+/Bi3+) with remarkable resistive switching effect for using in resistive random access memory (RRAM). Such kind of perovskites was prepared by partially substitution of Pb2+ with Bi3+ in a more popular compound CH 3 NH 3 PbBr 3. Consequently, RRAM devices based on the CH 3 NH 3 Pb 1− x Bi x Br 3 demonstrate an amazing high resistance switching ratio of about 105 and very low gate bias voltages of about ±1 V. Such appealing characteristics are even higher than those of frequently-used transition metal oxides perovskites like BaTiO 3 and SrZrO 3 , etc. The outstanding performance of CH 3 NH 3 Pb 1− x Bi x Br 3 will inspire the intensive research of such kind of feasibly obtained perovskites as electric storage materials. Organic-metallic halide perovskite CH 3 NH 3 PbMBr 3 ("M" refers to Pb2+ or the mixed Pb2+/Bi3+) with remarkable resistive switching effect are reported for using in resistive random access memory (RRAM). Image 1 • CH 3 NH 3 PbBr 3 ——great material for RRAM. • Doping Bi ion for more stable RRAM. • Enhancing the resistive switching effect through modifying the device structure. [ABSTRACT FROM AUTHOR]

The X‐site ion in organic–inorganic hybrid ABX3 perovskites (OHPs) varies from halide ion to bridging linkers like HCOO−, N3−, NO2−, and CN−. However, no nitrite‐based OHP ferroelectrics have been reported so far. Now, based on non‐ferroelectric [(CH3)4N][Ni(NO2)3], through the combined methodologies of quasi‐spherical shape, hydrogen bonding functionality, and H/F substitution, we have successfully synthesized an OHP ferroelectric, [FMeTP][Ni(NO2)3] (FMeTP=N‐fluoromethyl tropine). As an unprecedented nitrite‐based OHP ferroelectric, the well‐designed [FMeTP][Ni(NO2)3] undergoes the ferroelectric phase transition at 400 K with an Aizu notation of 6/mmmFm, showing multiaxial ferroelectric characteristics. This work is a great step towards not only enriching the molecular ferroelectric families but also accelerating the potential practical applications. [ABSTRACT FROM AUTHOR]

Recently, with the prevalence of 'perovskite fever', organic–inorganic hybrid perovskites (OHPs) have attracted intense attention due to their remarkable structural variability and highly tunable properties. In particular, the optical and electrical properties of organic–inorganic hybrid lead halides are typical of the OHP family. Besides, although three‐dimensional hybrid perovskites, such as [CH3NH3]PbX3 (X = Cl, Br or I), have been reported, the development of new organic–inorganic hybrid semiconductors is still an area in urgent need of exploration. Here, an organic–inorganic hybrid lead halide perovskite is reported, namely poly[(2‐azaniumylethyl)trimethylphosphanium [tetra‐μ‐bromido‐plumbate(II)]], {(C5H16NP)[PbBr4]}n, in which an organic cation is embedded in inorganic two‐dimensional (2D) mesh layers to produce a sandwich structure. This unique sandwich 2D hybrid perovskite material shows an indirect band gap of ∼2.700 eV. The properties of this compound as a semiconductor are demonstrated by a series of optical characterizations and indicate potential applications for optical devices. A twisted 2D layered anion structure is formed because of the infiltration of cations and the presence of hydrogen bonds. A band gap of ∼2.700 eV was found through experimental and theoretical studies. [ABSTRACT FROM AUTHOR]

Chemical modifications on aromatic spacers of 2D perovskites have been demonstrated to be an effective strategy to simultaneously improve optoelectronic properties and stability. However, its underlying mechanism is poorly understood. By using 2D phenyl-based perovskites ([C 6 H 5 (CH 2 ) m NH 3 ] 2 PbI 4 ) as models, the authors have revealed how the chemical nature of aromatic cations tunes the bandgap and charge transport of 2D perovskites by utilizing sum-frequency generation vibrational spectroscopy to determine the stacking arrangement and orientation of aromatic cations. It is found that the antiparallel slip-stack arrangement of phenyl rings between adjacent layers induces an indirect band gap, resulting in anomalous carrier dynamics. Incorporation of the CH 2 moiety causes stacking rearrangement of the phenyl ring and thus promotes an indirect to direct bandgap transition. In direct-bandgap perovskites, higher carrier mobility correlates with a larger orientation angle of the phenyl ring. Further optimizing the orientation angle by introducing a para-substituted element in a phenyl ring, higher carrier mobility is obtained. This work highlights the importance of leveraging stacking arrangement and orientation of the aromatic cations to tune the photophysical properties, which opens up an avenue for advancing high-performance 2D perovskites optoelectronics via molecular engineering., (© 2023 Wiley-VCH GmbH.)

Abstract Recent studies have shown that organic-inorganic hybrid perovskites (OIHPs) exhibit unprecedented optoelectronic properties for photovoltaic applications. Complete realizations of photo- and electrically induced surface polarization and recombination are critically important for extensively upgrading solar cell performance. We have explored such effects in a planar solar cell comprising ITO(glass)/PEDOT:PSS/CH 3 NH 3 PbI 3-x Cl x /PC 60 BM/PEI/Ag with a maximum power conversion efficiency (PCE) of 15.4%. A remarkable frequency-dependence of surface polarization was observed for the operating device under illumination (i.e. short-circuit current J s c condition) and at steady state (i.e. open-circuit voltage V o c condition). A sign reversal of the capacitance (i.e. negative capacitance) associated with the surface polarization and recombination was detected at some specific steady states. Based on capacitance-voltage (C - V) spectroscopic measurements and theoretical fittings, they can be understood that, (i) a naturally formed surface depletion region due to energy mismatch can be fully suppressed at a very low fluence and moderate forward bias voltage; (ii) a surface capacitance (C s) appears at lower ac -modulation frequencies only; (iii) remarkable trap-assist and band to band surface recombination may play the dominant roles for generating the negative capacitive effect in the CH 3 NH 3 PbI 3-x Cl x based photovoltaic system. Graphical abstract Image Highlights • Surface depletion region can be fully suppressed at low fluence and moderate bias voltage. • Surface capacitance (C s) appears at lower ac -modulation frequencies only. • Trap-assist and band to band surface recombination play dominant roles for negative capacitive effect in perovskite solar cells. [ABSTRACT FROM AUTHOR]

Abstract: Single crystals of methylammonium lead trihalide perovskites with high optical transparency and well‐defined facets are grown via solution process. Using these high‐quality crystals, the photocarrier‐induced refractive‐index change is observed for the first time in organic–inorganic hybrid perovskites. The photorefractive properties are measured using a laser interferometric technique that enables to monitor the time‐resolved refractive phase shifts. It is found that these phase shifts are determined by the initial density of photogenerated carriers and they are surprisingly retained even after carrier recombination. Utilizing the extremely long‐lived phase shift, it is demonstrated that the perovskite single crystal works as a phase shifter of laser light to generate any desired polarization. Furthermore, a periodic polarization‐modulation technique is established using the time‐dependent refractive phase shift. This refractive property can be used for advanced optical applications of organic–inorganic hybrid perovskites. [ABSTRACT FROM AUTHOR]

This paper reports a comparative study of thermal stability between all-organic metal halide perovskite (MHP) CsPbBr3and organic–inorganic hybrid MHP (methylammonium lead bromide MAPbBr3). The film morphology, crystal structure, steady-state photoluminescence intensity, and photoluminescence lifetime of CsPbBr3and MAPbBr3polycrystalline films were measured after thermal annealing at temperatures from 70°C to 230°C. The CsPbBr3films exhibited little change in their structural and luminescent properties after being annealed even at 230°C, whereas the MAPbBr3films exhibited a significant change in such properties due to their decomposition into PbBr2when annealed at ≥180°C. This study increased the understanding of the difference in the thermal stability of MHP polycrystalline films with different A-site cations. [ABSTRACT FROM PUBLISHER]

Recent advances in the use of organic-inorganic hybrid perovskites have been investigated in a variety of applications, such as solar cells, photodetectors, light-emitting devices, and lasers, because of their outstanding semiconductor properties. Furthermore, the perovskite structure can host extrinsic elements, making it a promising candidate for battery applications. Previous studies have shown that organic-inorganic hybrid perovskites can be suitable anode materials for both lithium- and sodium-ion batteries. However, multivalent rechargeable batteries with perovskite materials have not yet been realized. Herein, we studied the electrochemical performance of three-dimensional (CH 3 NH 3 PbI 3 (MAPbI 3) and long-chain alkylammonium (C 4 H 9 NH 3) 2 (CH 3 NH 3) 3 Pb 4 I 13 ((i BA) 2 (MA) 3 Pb 4 I 13) thin films as electrode materials for rechargeable Al-ion batteries. Our results showed that (i BA) 2 (MA) 3 Pb 4 I 13 presented a specific capacity of 257 mAh g–1 at a current density of 0.1 A g−1 and delivered 108 mAh g–1 after 250 cycles at a current density of 0.3 A g−1 with a retention of as high as 91 %, demonstrating a crucial role of isobutyl amine (C 4 H 9 NH 3) due to the unique hydrogen-bonding interaction of isobutyl amine that hinders the shuttle effect of polyiodide. The results open a new direction for the use of organic–inorganic hybrid perovskites for new secondary aluminum ion batteries. [Display omitted] • We studied the electrochemical performance of 3D and LCA organic–inorganic hybrid perovskite thin films as electrode materials for rechargeable Al-ion batteries. • The LCA electrode yielded a specific capacity of 257 mAh g–1 at a current density of 0.1 A g−1 and delivered 108 mAh g–1 after 250 cycles at a current density of 0.3 A g−1 with a retention of as high as 91%. • The excellent performance can be attributed to the unique hydrogen-bonding interaction of isobutylamine, which effectively hindered the shuttle effect of polyiodide, as confirmed by ex-situ FT-IR, Raman, XPS, ESI-MS, and DFT calculations. [ABSTRACT FROM AUTHOR]

We analyze the behavior of a series of newly synthesized (R-NH3)2PbX4 perovskites and, in particular, discuss the possible reasons which cause their degradation under UV illumination. Experimental results show that the degradation process depends a lot on their molecular components: not only the inorganic part, but also the chemical structure of the organic moieties play an important role in bleaching and photo-chemical reaction processes which tend to destroy perovskites luminescent framework. In addition, we find the spatial arrangement in crystal also influences the photostability course. Following these trends, we propose a plausible mechanism for the photodegradation of the films, and also introduced options for optimized stability.

Organic−inorganic hybrid perovskites with well-defined morphology have attracted much attention due to their unique photophysical properties. However, controlling the morphology of nanocrystalline perovskite to improve its photoelectric application remains a challenge. In this article, using a modified solution deposition method, we successfully synthesized uniform methylammonium lead iodide (MAPbI3) nanoplates, nanocubes, and nanorods and investigated the effect of morphology on the photoelectric properties of these materials. We found that the morphology can be controlled by regulating the amounts of reactant methylammonium iodide (MAI) and the rate at which MAPbI3 precursor is added into toluene solution, and that the corresponding size distributions can be optimized by tuning the final vacuum-drying temperature. The morphology has an obvious effect on the bandgap optimization and fluorescence enhancement of MAPbI3, and the nanoplates exhibit stronger photoluminescence intensity and have a longer carrier lifetime than nanocubes and nanorods. The results show that the morphologies of MAPbI3 perovskite nanocrystals can be controlled by tuning the synthesizing conditions, and the MAPbI3 perovskite nanocrystals with special morphology can be used in special nanosize optoelectronic devices.

Organic-inorganic hybrid perovskites have attracted extensive interest in recent years due to their remarkable properties in highly efficient solar cells. The quality of the perovskite thin films has been identified as a critical factor to affect the performances of the solar cells. To achieve uniform and dense perovskite films, many efforts have been attempted on controlling the crystallinity of the particles, grain size, as well as surface coverage. Using organic coupling agents to connect the mesoporous TiO2 with the perovskite film is an effective way to guide the growth of perovskite film. However, the influences of organic molecular configurations on the perovskite crystallization are still not being well studied. In this article, two amino acids, 4-aminobenzoic acid and 4-aminobutyric acid, are employed with similar molecular size and closed chain length to study the molecular rigidity of the organic coupling agents affecting the quality of perovskite films. Greatly improved perovskite film has been obtained with the template effect of rigid 4-aminobenzoic acid and thus the cell performance has been significantly increased. [ABSTRACT FROM AUTHOR]

The control of the composition of mixed organic-inorganic hybrid perovskites by solid-state alloying is a very efficient tool to tune the band gap of the material, leading to enhanced optical performances. At this end, we have elaborated a series of mixed-halide two-dimensional hybrid perovskites (C 6 H 11 NH 3 ) 2 [PbBr 4−x I x ], with 0 ≤ x ≤ 4, for which we studied the composition-dependence of the structural parameters and their effect on the white-light luminescence properties at room temperature. The structural analysis revealed the existence of a composition-induced structural phase transition occurring in the range 2 < x < 2.4, associated to a change between Cmc 2 1 and Pbca space groups. The optical properties, investigated using optical absorption and photoluminescence measurements, have shown that bromine (Br) to iodine (I) halogen ion substitution redshifts the excitonic optical absorption band, as a result of the hybridization of the valence band structure, built from np orbitals of Br and/or I halogens and 6s orbitals of lead. When iodine was predominant (x > 2), the photoluminescence spectra showed a sharp peak with a relatively small Stokes shift (less than 0.2 eV) attributed to free or bound excitons emissions. In contrast, when the bromide is majority (x < 2), the photoluminescence response consists in a broadband white-light emission with a very large Stokes shift (between 1.2 eV and 0.3 eV), attributed to self-trapped excitons activated by a strong structural distortion of the inorganic sheets. Confronting optical and structural data highlighted the effect of the structure in monitoring the optical properties, since the intensity of the white-light emission increases with the bromine content and was found to excellently correlate with the change of the angular distortion of inorganic octahedra PbX 6 (X = I/Br). [ABSTRACT FROM AUTHOR]

High-efficiency electromagnetic (EM) functional materials are the core building block of high-performance EM absorbers and devices, and they are indispensable in various fields ranging from industrial manufacture to daily life, or even from national defense security to space exploration. Searching for high-efficiency EM functional materials and realizing high-performance EM devices remain great challenges. Herein, a simple solution-process is developed to rapidly grow gram-scale organic-inorganic (MAPbX 3 , X = Cl, Br, I) perovskite microcrystals. They exhibit excellent EM response in multi bands covering microwaves, visible light, and X-rays. Among them, outstanding microwave absorption performance with multiple absorption bands can be achieved, and their intrinsic EM properties can be tuned by adjusting polar group. An ultra-wideband bandpass filter with high suppression level of -71.8 dB in the stopband in the GHz band, self-powered photodetectors with tunable broadband or narrowband photoresponse in the visible-light band, and a self-powered X-ray detector with high sensitivity of 3560 µC Gy air -1  cm -2  in the X-ray band are designed and realized by precisely regulating the physical features of perovskite and designing a novel planar device structure. These findings open a door toward developing high-efficiency EM functional materials for realizing high-performance EM absorbers and devices., (© 2023 Wiley-VCH GmbH.)

Transmission electron microscopy (TEM) is a powerful tool for unveiling the structural, compositional, and electronic properties of organic-inorganic hybrid perovskites (OIHPs) at the atomic to micrometer length scales. However, the structural and compositional instability of OIHPs under electron beam radiation results in misunderstandings of the microscopic structure-property-performance relationship in OIHP devices. Here, ultralow dose TEM is utilized to identify the mechanism of the electron-beam-induced changes in OHIPs and clarify the cumulative electron dose thresholds (critical dose) of different commercially interesting state-of-the-art OIHPs, including methylammonium lead iodide (MAPbI 3 ), formamidinium lead iodide (FAPbI 3 ), FA 0.83 Cs 0.17 PbI 3 , FA 0.15 Cs 0.85 PbI 3 , and MAPb 0.5 Sn 0.5 I 3 . The critical dose is related to the composition of the OIHPs, with FA 0.15 Cs 0.85 PbI 3 having the highest critical dose of ≈84 e Å -2 and FA 0.83 Cs 0.17 PbI 3 having the lowest critical dose of ≈4.2 e Å -2 . The electron beam irradiation results in the formation of a superstructure with ordered I and FA vacancies along <110> c , as identified from the three major crystal axes in cubic FAPbI 3 , <100> c , <110> c , and <111> c . The intragrain planar defects in FAPbI 3 are stable, while an obvious modification is observed in FA 0.83 Cs 0.17 PbI 3 under continuous electron beam exposure. This information can serve as a guide for ensuring a reliable understanding of the microstructure of OIHP optoelectronic devices by TEM., (© 2023 Wiley-VCH GmbH.)