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Several studies have demonstrated that low-dimensional structures (e.g., two-dimensional (2D)) associated with three-dimensional (3D) perovskite films enhance the efficiency and stability of perovskite solar cells. Here, we aim to track the formation sites of the 2D phase on top of the 3D perovskite and to establish correlations between molecular stiffness and steric hindrance of the organic cations and their influence on the formation and crystallization of 2D/3D. Using cathodoluminescence combined with a scanning electron microscopy technique, we verified that the formation of the 2D phase occurs preferentially on the grain boundaries of the 3D perovskite. This helps explain some passivation mechanisms conferred by the 2D phase on 3D perovskite films. Furthermore, by employing in situ grazing-incidence wide-angle X-ray scattering, we monitored the formation and crystallization of the 2D/3D perovskite using three cations with varying molecular stiffness. In this series of molecules, the formation and crystallization of the 2D phase are found to be dependent on both steric hindrance around the ammonium group and molecular stiffness. Finally, we employed a 2D/3D perovskite heterointerface in a solar cell. The presence of the 2D phase, particularly those formed from flexible cations, resulted in a maximum power conversion efficiency of 21.5%. This study provides insight into critical aspects related to how bulky organic cations' stiffness and steric hindrance influence the formation, crystallization, and distribution of 2D perovskite phases.

Metal halide perovskites (MHPs) are low-temperature processable hybrid semiconductor materials with exceptional performances that are revolutionizing the field of optoelectronic devices. Despite their great potential, commercial deployment is hindered by MHPs lack of stability and durability, mainly attributed to ion migration and chemical interactions with the electrodes. To address these issues, 2D layered MHPs are investigated as possible device interlayers or active material substitutes. Here, the 2D perovskite (PEA)2PbBr4 is considered that is recently discussed as promising candidate for X-ray direct detection. While the increased resilience of (PEA)2PbBr4 radiation detectors has already been reported, the physical mechanisms responsible for such improvement compared to 3D perovskites are not still fully understood. To unravel the charge transport process in (PEA)2PbBr4 crystals thought to underly the device better performance, an investigation technique is adapted previously used on highly resistive inorganic semiconductors, called photo induced current transient spectroscopy (PICTS). It is demonstrated that PICTS can reliably detect three trap states (T1, T2, and T3), and that their evolution upon X-ray exposure can explain (PEA)2PbBr4 superior radiation tolerance and reduced aging effects. Overall, the results provide essential insights into the electrical characteristics of 2D perovskites and their potential application as reliable direct X-ray detectors.

The introduction of chiral organic spacers in low-dimensional metal-halide perovskites triggers chiroptical activity, which is appealing for spintronic applications. However, a comprehensive understanding of structure formation and the ability to control phase purity in such materials have yet to be developed. Herein, the impact of processing conditions on the phase purity, microstructure, and chiroptical properties of chiral 2D perovskites is explored. The anisotropic emergence of a 1D perovskite inside the 2D matrix and its dependence on the organic cation chirality, solvent, and thermal annealing conditions are shown. By controlling these parameters, the in-plane conductivity of the films is nearly doubled. Furthermore, it is demonstrated, for the first time, that solvent choice and the spatial configuration of the organic cation can have an impact on the residual lattice strain and the energetic disorder of the system. The fundamentals presented here can help to improve the film deposition methods for low-dimensional chiral perovskites, offering strategies to control phase purity.

Metal halide perovskites (MHPs) are low‐temperature processable hybrid semiconductor materials with exceptional performances that are revolutionizing the field of optoelectronic devices. Despite their great potential, commercial deployment is hindered by MHPs lack of stability and durability, mainly attributed to ion migration and chemical interactions with the electrodes. To address these issues, 2D layered MHPs are investigated as possible device interlayers or active material substitutes. Here, the 2D perovskite (PEA)2PbBr4 is considered that is recently discussed as promising candidate for X‐ray direct detection. While the increased resilience of (PEA)2PbBr4 radiation detectors has already been reported, the physical mechanisms responsible for such improvement compared to 3D perovskites are not still fully understood. To unravel the charge transport process in (PEA)2PbBr4 crystals thought to underly the device better performance, an investigation technique is adapted previously used on highly resistive inorganic semiconductors, called photo induced current transient spectroscopy (PICTS). It is demonstrated that PICTS can reliably detect three trap states (T1, T2, and T3), and that their evolution upon X‐ray exposure can explain (PEA)2PbBr4 superior radiation tolerance and reduced aging effects. Overall, the results provide essential insights into the electrical characteristics of 2D perovskites and their potential application as reliable direct X‐ray detectors. [ABSTRACT FROM AUTHOR]

The stability of hybrid organic–inorganic halide perovskite semiconductors remains a significant obstacle to their application in photovoltaics. To this end, the use of low‐dimensional (LD) perovskites, which incorporate hydrophobic organic moieties, provides an effective strategy to improve their stability, yet often at the expense of their performance. To address this limitation, supramolecular engineering of noncovalent interactions between organic and inorganic components has shown potential by relying on hydrogen bonding and conventional van der Waals interactions. Here, the capacity to access novel LD perovskite structures that uniquely assemble through unorthodox S‐mediated interactions is explored by incorporating benzothiadiazole‐based moieties. The formation of S‐mediated LD structures is demonstrated, including one‐dimensional (1D) and layered two‐dimensional (2D) perovskite phases assembled via chalcogen bonding and S–π interactions. This involved a combination of techniques, such as single crystal and thin film X‐ray diffraction, as well as solid‐state NMR spectroscopy, complemented by molecular dynamics simulations, density functional theory calculations, and optoelectronic characterization, revealing superior conductivities of S‐mediated LD perovskites. The resulting materials are applied in n‐i‐p and p‐i‐n perovskite solar cells, demonstrating enhancements in performance and operational stability that reveal a versatile supramolecular strategy in photovoltaics. [ABSTRACT FROM AUTHOR]

Despite the significant progress of blue perovskite light‐emitting diodes (PeLEDs) in recent years, huge challenges still remain in improving their efficiency and spectral stability. In this work, a new strategy is reported to realize efficient and spectral stable blue PeLEDs through synchronously optimizing light outcoupling and carrier recombination of perovskite films. By introducing additives in both precursor solution and antisolvent, the crystallization of the perovskite films is regulated, leading to a spontaneous formation of undulant morphology, which favorably enhances the light outcoupling efficiency. Meanwhile, the formation of low‐dimensional perovskite phases is suppressed, in accompany with a reduced defect density and accelerated energy transfer, leading to a rapid concentration of excitons in the target perovskite phases and a significant enhancement of radiative carrier recombination. Resultantly, the optimized blue perovskite films show a high photoluminescent quantum yield approaching 80%, and the corresponding optimized PeLEDs show a high external quantum efficiency (EQE) of 11.88%, which significantly outperforms the control device with only 1.96%. Importantly, the optimized perovskite films and PeLEDs also exhibit improved spectral stability. This work provides a new pathway toward realizing efficient and spectral‐stable PeLEDs via simultaneously tackling the issues of light outcoupling and carrier recombination in the devices. [ABSTRACT FROM AUTHOR]

Converting PbI2 residues into low‐dimensional perovskites through post‐treatment with ammonium‐based large cations can passivate 3D perovskites, thus has emerged as an effective strategy to improve the performance of perovskite solar cells (PSCs). Herein, a dramatically improved efficiency is demonstrated for PSCs based on a two‐step‐processed FAPbI3 perovskite via post‐treatment with formamidinium (FA)‐based benzamidine hydrochloride (PFACl), outperforming the commonly used methylamine (MA)‐based benzylamine hydrochloride (PMACl). With an in‐depth exploration of the crystal structures and morphology changes of the FAPbI3 perovskite upon the PFACl post‐treatment, the preferential formation of 1D rather than 2D structures on the 3D perovskite film is identified. In contrast to the 2D counterpart, the more energetically favorable 1D structure enables a more effective elimination of PbI2 residues. As a consequence, the PFACl‐induced 1D/3D perovskite film is endowed with smoother morphology, more uniform surface potential distribution, lower trap density, faster charge transfer, and better film stability than the PMACl‐induced 2D/3D perovskite and control films, demonstrating champion efficiencies of 24.9% for a small‐size PSC, 23.6% for a 1 cm2 large‐size PSC, and 21.2% for a 5 × 5 cm2 mini‐module, which is the highest among the perovskite solar mini‐modules using the two‐step deposition method. [ABSTRACT FROM AUTHOR]

Low-dimensional perovskite (PVK) materials have attracted significant research interest, because of their quantum-confined effect, tunable band gap structures, and higher stability than that of three-dimensional (3D) PVKs. In semiconductor optoelectronic devices, high speed and small size are closely interlinked. The development of high-speed devices requires researchers to fully understand the properties of materials, especially the dynamic processes such as carrier recombination, separation, and transport, which often play a crucial role in the performance of devices. As an indispensable part of dynamic research, spin relaxation is also of great significance in studying the properties of materials and explore possible applications. Lead halide PVK materials have strong spin-orbit coupling (SOC), which provides a basis for information storage and processing by using spin degrees of freedom. Therefore, studying the carrier and spin dynamics of low-dimensional PVKs is an effective way to understand the internal properties of low-dimensional PVKs clearly. This paper summarizes the latest research progress on the ultrafast carrier and spin dynamics in low-dimensional PVKs, to comprehensively understand their carrier and spin behaviors and present an outlook for relevant studies in this area. [ABSTRACT FROM AUTHOR]

Low-dimensional all-inorganic metal halide perovskites (MHPs) have attracted attention due to their promising advantages as semiconductor materials for optoelectronic applications. However, obtaining a low-dimensional MHPs pure phase has been difficult due to its high ionic nature. Here, the one-step in-situ deposition of CsPb 2 Cl 5 films by Aerosol Assisted Chemical Vapor Deposition (AACVD) is reported for the first time. An analysis of the effects of precursor concentrations, using ethanol (EtOH) as antisolvent, and Yb3+ doping on the resulting three-dimensional and/or two-dimensional perovskite phase films is presented. It was found that a lead rich precursor (PbCl 2 :CsCl = 2:1) was necessary to promote the formation of the CsPb 2 Cl 5 phase, in addition, the use of EtOH and doping with hetero-valent Yb3+ ions was required to attain this phase successfully. The excitation and emission photoluminescence spectra analysis for these films is focused on the three principal emissions: i) a narrow emission peak around 418 nm from the CsPbCl 3 phase, ii) a dual broad emission around 550 nm from the CsPb 2 Cl 5 phase, and iii) an emission at 984 nm associated with the Yb3+ ions introduced as dopants in the MHPs lattice. A possible mechanism is proposed for the observed energy transfer from the CsPb 2 Cl 5 matrix to the ytterbium ions and for the interactions between Yb3+ and the excitonic emissions. [ABSTRACT FROM AUTHOR]

Flexible perovskite solar cells are lightweight, bendable, and applicable to curved surfaces. Polyethylene terephthalate (PET) has become the substrate of choice compared to other plastic substrates like polyethylene naphthalate. PET is not only stable but also much cheaper to manufacture, an important factor for photovoltaics (PV). Herein, highly efficient devices on PET are demonstrated using a dual low‐temperature (≤100 °C) approach, first by anion mixing (replacing I with Br) of the lead‐containing perovskite composition, increasing bandgap (42% improvement), and then by interfacial engineering with tetrabutylammonium bromide (TBAB) (a further 26% improvement), reaching efficiencies of 28.9% at 200 lx and a record 32.5% at 1000 lx. The TBA+ cation intercalates into the structure, substituting formamidinium cations at the perovskite/TBAB interface, inducing the formation of large‐sized, lower dimensional structures over the 3D perovskite matrix. The resulting PV cell has 1.4 times higher carrier lifetime, one order of magnitude lower leakage currents, and 3 times lower defect densities, suppressing recombination. Importantly, stability (ISOS‐D1 protocol) improves by more than double with treatment. Highly efficient and stable cells on PET films enable seamless integration with wearable, portable, smart building, and Internet of Things electronic devices, expanding the reach of indoor applications. [ABSTRACT FROM AUTHOR]

Low‐dimensional perovskites (LDPs) have attracted significant attention due to their high stability, great chemical flexibility, and fertile "playground" for structural modulation, which are expected to herald the next‐generation multifunctional devices. While there is a high diversity of LDPs in the literature, the organic cations in most of the literature are still limited to amines. Here, the preparation of centimeter‐sized LDP single crystals with amidino‐based spacers is described, which enables systematic investigations on how halides initiate different structural stacking and on their physical properties. The 4‐amidinopyridine (4AP) cation in (4AP)PbX4 (X = Br, I) is vertically distributed between the inorganic layers to form a two‐dimensional perovskite. While the Cl‐based exhibits one‐dimensional perovskitoid packing. The change of halogens from Cl to Br and I leads to a lower hydrogen bonding, hardness and activation energy of the crystal. Finally, the potential of these crystals for X‐ray detectors is demonstrated. The (4AP)PbBr4 device achieves the highest sensitivity among three devices (373.1 µC Gyair−1 cm−2, 10 V), benefiting from the balanced charge transport and ionic migration. It is anticipated that this work will lead to further studies on the exploration and physics of novel LDP with properties suitable for radiation detection. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have emerged as low-cost photovoltaic representatives. Constructing three-dimensional (3D)/two-dimensional (2D) perovskite heterostructures has been shown to effectively enhance the efficiency and stability of PSCs. However, further enhancement of device performance is still largely limited by inferior conductivity of the 2D perovskite capping layer and its mismatched energy level with the 3D perovskite layer. Here, we developed an effective surface modification strategy via synergically incorporating inorganic high valence-state niobium ion (Nb 5+ ) metal dopants and organic ammonium halide salts to in situ construct a high-quality 2D perovskite capping layer on top of the underlying 3D perovskite layer. As a result, the conductivity of the 2D perovskite capping layer was effectively enhanced by 43%, the energy barrier between 3D and 2D perovskite layers was favorably reduced, and the built-in electric field of the 3D/2D heterostructured perovskite stacks has been enlarged. In addition, the 2D perovskite capping layer also effectively reduced the defect densities by up to 29%, as verified by the space-charge-limited-current (SCLC) tests. Benefiting from the facilitated charge extraction and suppressed non-radiative recombination, the blade-coated hole transport layer-free PSCs based on this optimized 3D/2D heterostructured perovskite film achieved an efficiency of 23.2%, ∼19% higher than that of the control device (19.5%), which represented one of the best-performing PSCs with simplified device architecture fabricated via a scalable fabrication technique. The modified 3D/2D perovskite-based device also exhibited improved operational stability.

Direct understanding of the formation and crystallization of low-dimensional (LD) perovskites with varying dimensionalities employing the same bulky cations can offer insights into LD perovskites and their heterostructures with 3D perovskites. In this study, the secondary amine cation of N-methyl-1-(naphthalen-1-yl)methylammonium (M-NMA + ) and the formation dynamics of its corresponding LD perovskite are investigated. The intermolecular π-π stacking of M-NMA + and their connection with inorganic PbI 6 octahedrons within the product structures control the formation of LD perovskite. In an N,N-dimethylformamide (DMF) precursor solution, both 1D and 2D products can be obtained. Interestingly, due to the strong interaction between M-NMA + and the DMF solvent, compared to the 1D phase, the formation of 2D perovskites is uniquely dependent on heterogeneous nucleation. Nevertheless, post-treatment of 3D perovskite films with an isopropanol solution of M-NMAI leads to the exclusive formation of thermally stable 1D phases on the surface. The resulting 1D/3D heterostructure facilitates perovskite solar cells (PSCs) to not only achieve a record efficiency of 25.51% through 1D perovskite passivation but also significantly enhance the thermal stability of unencapsulated devices at 85 °C. This study deepens the understanding of the formation dynamics of LD perovskites and offers an efficient strategy for fabricating stable and high-performance PSCs., (© 2025 Wiley‐VCH GmbH.)

3D hybrid perovskites (APbX3) have made a significant impact on the field of optoelectronic materials due to their excellent performance combined with facile solution deposition and up‐scalable device fabrication. Nonetheless, these materials suffer from environmental instability. To increase material stability, the organic cation (A) is substituted by the non‐volatile cesium cation. However, the desired photoactive cesium lead(II) iodide black phase is metastable in ambient conditions and spontaneously converts into the photo‐inactive yellow δ‐phase. In this work, the black phase is stabilized by the formation of a quasi‐2D perovskite containing a benzothieno[3,2‐b]benzothiophene (BTBT) large organic ammonium cation. Thermal analysis shows that degradation of the butylammonium (BA)‐based quasi‐2D perovskite (BA)2CsPb2I7 sets in at ≈130 °C, while (BTBT)2CsPb2I7 is phase‐stable until ≈230 °C. Additionally, the (BTBT)2CsPb2I7 film does not show any sign of degradation after exposure to 77% Relative Humidity in the dark for 152 days, while (BA)2CsPb2I7 degrades in a single day. Photoconductor‐type detectors based on (BTBT)2CsPb2I7 demonstrate an increased external quantum efficiency and a similar specific detectivity compared to the BA‐based reference detectors. The results demonstrate the utility of employing a BTBT cation within the organic layer of quasi‐2D perovskites to significantly enhance the stability while maintaining the optoelectronic performance. [ABSTRACT FROM AUTHOR]

Abstract Metal halide perovskites possess appealing optoelectronic properties and have been widely applied for solar energy harvesting and light emitting. Although perovskite solar cells (PeSCs) and perovskite light‐emitting diodes (PeLEDs) have been developed rapidly in recent years, there are still no universal rules for the selection of perovskites to achieve high‐performance optoelectronic devices. In this review, the working mechanisms of PeSCs and PeLEDs are first demonstrated with the discussion on the factors which determine the device performance. We then examine the optoelectronic properties of perovskites with structures modulated from 3D, 2D, 1D to 0D, and analyze the corresponding structure‐property relationships in terms of photo‐electric and electric‐photo conversion processes. Based on the unique optoelectronic properties of structurally modulated perovskites, we put forward the concept of structural assembling engineering that integrate the merits of different types of perovskites within one matrix and elaborate their excellent properties for applications of both PeSCs and PeLEDs. Finally, we discuss the potential challenges and provide our perspectives on the structural assembling engineering of perovskites for future optoelectronic applications.

Low‐dimensional (LD) perovskites can effectively passivate and stabilize 3D perovskites for high‐performance perovskite solar cells (PSCs). Regards CsPbI3‐based PSCs, the influence of high‐temperature annealing on the LD perovskite passivation effect has to be taken into account due to fact the black‐phase CsPbI3 crystallization requires high‐temperature treatment, however, which has been rarely concerned so far. Here, the thermal stability of LD perovskites based on three hydrophobic organic ammonium salts and their passivation effect toward CsPbI3 and the whole device performance, have been investigated. It is found that, phenyltrimethylammonium iodide (PTAI) and its corresponding LD perovskites exhibit excellent thermal stability. Further investigation reveals that PTAI‐based LD perovskites are mainly distributed at grain boundaries, which not only enhances the phase stability of CsPbI3 but also effectively suppresses non‐radiative recombination. As a consequence, the champion PSC device based on CsPbI3 exhibits a record efficiency of 21.0 % with high stability. [ABSTRACT FROM AUTHOR]

In view of their excellent luminescence properties, nanocrystalline metal halide perovskites have diverse optoelectronic applications, including those related to anticounterfeiting. However, high‐quality optical anticounterfeiting typically requires multiple encryptions relying on several optical modes to ensure information security. Herein, an efficient anticounterfeiting strategy based on dual optical encryption is realized by combining up‐ and downconversion luminescence in a nanocomposite with NaYF4 : Er3+,Yb3+ as core and a CsMnCl3 as shell. The emission color of this nanocomposite depends on the penetration depth of incident radiation and can be changed by varying the excitation source (980 nm laser or UV light) to produce different luminescent patterns. This feature allows one to effectively improve the anticounterfeiting index and fabricate professional anticounterfeiting materials. [ABSTRACT FROM AUTHOR]

Abstract Perovskite materials in different dimensions show great potential in direct X‐ray detection, but each with limitations stemming from its own intrinsic properties. Particularly, the sensitivity of two‐dimensional (2D) perovskites is limited by poor carrier transport while ion migration in three‐dimensional (3D) perovskites causes the baseline drifting problem. To circumvent these limitations, herein a double‐layer perovskite film is developed with properly aligned energy level, where 2D (PEA)2MA3Pb4I13 (PEA=2‐phenylethylammonium, MA=methylammonium) is cascaded with vertically crystallized 3D MAPbI3. In this new design paradigm, the 3D layer ensures fast carrier transport while the 2D layer mitigates ion migration, thus offering a high sensitivity and a greatly stabilized baseline. Besides, the 2D layer increases the film resistivity and enlarges the energy barrier for hole injection without compromising carrier extraction. Consequently, the double‐layer perovskite detector delivers a high sensitivity (1.95 × 104 μC Gyair−1 cm−2) and a low detection limit (480 nGyair s−1). Also demonstrated is the X‐ray imaging capacity using a circuit board as the object. This work opens up a new avenue for enhancing X‐ray detection performance via cascade assembly of various perovskites with complementary properties.

Metal halide perovskites possess appealing optoelectronic properties and have been widely applied for solar energy harvesting and light emitting. Although perovskite solar cells (PeSCs) and perovskite light‐emitting diodes (PeLEDs) have been developed rapidly in recent years, there are still no universal rules for the selection of perovskites to achieve high‐performance optoelectronic devices. In this review, the working mechanisms of PeSCs and PeLEDs are first demonstrated with the discussion on the factors which determine the device performance. We then examine the optoelectronic properties of perovskites with structures modulated from 3D, 2D, 1D to 0D, and analyze the corresponding structure‐property relationships in terms of photo‐electric and electric‐photo conversion processes. Based on the unique optoelectronic properties of structurally modulated perovskites, we put forward the concept of structural assembling engineering that integrate the merits of different types of perovskites within one matrix and elaborate their excellent properties for applications of both PeSCs and PeLEDs. Finally, we discuss the potential challenges and provide our perspectives on the structural assembling engineering of perovskites for future optoelectronic applications. [ABSTRACT FROM AUTHOR]

Perovskite materials in different dimensions show great potential in direct X‐ray detection, but each with limitations stemming from its own intrinsic properties. Particularly, the sensitivity of two‐dimensional (2D) perovskites is limited by poor carrier transport while ion migration in three‐dimensional (3D) perovskites causes the baseline drifting problem. To circumvent these limitations, herein a double‐layer perovskite film is developed with properly aligned energy level, where 2D (PEA)2MA3Pb4I13 (PEA=2‐phenylethylammonium, MA=methylammonium) is cascaded with vertically crystallized 3D MAPbI3. In this new design paradigm, the 3D layer ensures fast carrier transport while the 2D layer mitigates ion migration, thus offering a high sensitivity and a greatly stabilized baseline. Besides, the 2D layer increases the film resistivity and enlarges the energy barrier for hole injection without compromising carrier extraction. Consequently, the double‐layer perovskite detector delivers a high sensitivity (1.95 × 104μC Gyair−1 cm−2) and a low detection limit (480 nGyair s−1). Also demonstrated is the X‐ray imaging capacity using a circuit board as the object. This work opens up a new avenue for enhancing X‐ray detection performance via cascade assembly of various perovskites with complementary properties. [ABSTRACT FROM AUTHOR]

Abstract With only a few deep-level defect states having a high formation energy and dominance of shallow carrier non-trapping defects, the defect-tolerant electronic and optical properties of lead halide perovskites have made them appealing materials for high-efficiency, low-cost, solar cells and light-emitting devices. As such, recent observations of apparently deep-level and highly luminescent states in low-dimensional perovskites have attracted enormous attention as well as intensive debates. The observed green emission in 2D CsPb2Br5 and 0D Cs4PbBr6 poses an enigma over whether it is originated from intrinsic point defects or simply from highly luminescent CsPbBr3 nanocrystals embedded in the otherwise transparent wide band gap semiconductors. The nature of deep-level edge emission in 2D Ruddlesden–Popper perovskites is also not well understood. In this mini review, the experimental evidences that support the opposing interpretations are analyzed, and challenges and root causes for the controversy are discussed. Shortcomings in the current density functional theory approaches to modeling of properties and intrinsic point defects in lead halide perovskites are also noted. Selected experimental approaches are suggested to better correlate property with structure of a material and help resolve the controversies. Understanding and identification of the origin of luminescent centers will help design and engineer perovskites for wide device applications.

Abstract Replacing methylammonium (MA+), formamidine (FA+), and/or cesium (Cs+) in 3D metal halide perovskites by larger organic cations have built a series of low‐dimensional metal halide perovskites (LDMHPs) in which the inorganic metal halide octahedra arranging in the forms of 2D layers, 1D chains, and 0D points. These LDMHPs exhibit significantly different optoelectronic properties from 3D metal halide perovskites (MHPs) due to their unique quantum confinement effects and large exciton binding energies. In particular, LDMHPs often have excellent broadband luminescence from self‐trapped excitons. Chemical composition, hydrogen bonding, and external factors (temperature and pressure etc.) determine structures and influence photoelectric properties of LDMHPs greatly, and especially it seems that there is no definite regulation to predict the structure and photoelectric properties when a random cation, metal, and halide is chosen to design a LDMHP. Therefore, this review discusses the construction strategies of the recent reported LDMHPs and their application progress in the luminescence field for a better understanding of these factors and a prospect for LDMHPs’ development in the future.

Replacing methylammonium (MA+), formamidine (FA+), and/or cesium (Cs+) in 3D metal halide perovskites by larger organic cations have built a series of low‐dimensional metal halide perovskites (LDMHPs) in which the inorganic metal halide octahedra arranging in the forms of 2D layers, 1D chains, and 0D points. These LDMHPs exhibit significantly different optoelectronic properties from 3D metal halide perovskites (MHPs) due to their unique quantum confinement effects and large exciton binding energies. In particular, LDMHPs often have excellent broadband luminescence from self‐trapped excitons. Chemical composition, hydrogen bonding, and external factors (temperature and pressure etc.) determine structures and influence photoelectric properties of LDMHPs greatly, and especially it seems that there is no definite regulation to predict the structure and photoelectric properties when a random cation, metal, and halide is chosen to design a LDMHP. Therefore, this review discusses the construction strategies of the recent reported LDMHPs and their application progress in the luminescence field for a better understanding of these factors and a prospect for LDMHPs' development in the future. [ABSTRACT FROM AUTHOR]

There is an ongoing surge of interest in the use of formamidinium (FA) lead iodide perovskites in photovoltaics due to their exceptional optoelectronic properties. However, thermodynamic instability of the desired cubic perovskite (α‐FAPbI3) phase at ambient conditions leads to the formation of a yellow non‐perovskite (δ‐FAPbI3) phase that compromises its utility. A stable α‐FAPbI3 perovskite phase is achieved by employing benzylammonium iodide (BzI) and the microscopic structure is elucidated by using solid‐state NMR spectroscopy and X‐ray scattering measurements. Perovskite solar cells based on the FAPbI3(BzI)0.25 composition achieve power conversion efficiencies exceeding 20%, which is accompanied by enhanced shelf‐life and operational stability, maintaining 80% of the performance after one year at ambient conditions. [ABSTRACT FROM AUTHOR]

Low‐dimensional halide perovskites with excellent luminescent properties have become leading candidates for optoelectronic and radiation‐detection applications. In this work, Tl cation is incorporated into 0D perovskite Cs3Cu2I5 host and an ultrabright and efficient scintillator is developed for X‐ray and γ‐ray detection. The Tl‐doped Cs3Cu2I5 crystals exhibit a high photoluminescence quantum efficiency of 79.2%. The radioluminescence emission of Cs3Cu2I5:Tl crystal under X‐ray excitation consists of a self‐trapped exciton emission at 440 nm and a Tl‐related emission at 510 nm at room temperature. With optimized Tl doping, the Cs3Cu2I5 not only demonstrates about five‐times enhanced steady‐state scintillation yield up to 150 000 photons/MeV and an improvement of X‐ray detection limit from 103.6 to 66.3 nGy s−1, but also maintains an extremely low afterglow of 0.17% at 10 ms after X‐ray cut‐off. The Cs3Cu2I5:Tl also possess a remarkable energy resolution of 3.4% at 662 keV and an ultrahigh light yield of 87 000 photons/MeV under 137Cs γ‐ray radiation. [ABSTRACT FROM AUTHOR]

The reactions of lead bromide with 7,7,8,8-tetracyanoquinodimethane and anthracen-9-ylmethanamine hydrobromide in dimethylformamide (DMF) afford the known low-dimensional perovskite {PbBr2(DMF)}n (I) with an impurity of a new hybrid 1D perovskite {Ca(DMF)6[PbBr3]2}n (II), which is isolated in the individual form and characterized by X-ray diffraction analysis. In the crystal of compound II, lead bromide forms infinite chains of PbBr5 octahedra with one vacant vertex between which calcium cations coordinated by the DMF molecules are arranged. The calcium cations presumably have got into the reaction mixture from water used for the washing of the reaction vessel for crystallization after the previous attempt of the synthesis. An attempt of the purposeful preparation of this hybrid 1D perovskite from various calcium salts as sources of this metal ion gives one more new low-dimensional perovskite {Ca(DMF)6[PbBr2.3Cl0.7]2}n (III) in which halide anions (bromide and chloride anions from lead bromide and calcium chloride, respectively) build up the coordination sphere of the lead ion to an octahedral one inducing no noticeable changes in the crystal packing compared to that of compound II. The X-ray diffraction results are deposited with the Cambridge Crystallographic Data Centre (CIF files CCDC nos. 2045586 (I), 2047219 (II), and 2047220 (III)). [ABSTRACT FROM AUTHOR]

Carbon-based perovskite solar cells (C-PSCs) have the advantages of low-cost and high-stability, but their photovoltaic performance is limited by severe defect-induced recombination and low hole extraction efficiency. 1D perovskite is proven to effectively passivate the defects on the perovskite surface, therefore reducing non-radiative recombination loss. However, the unsuitable energy level of most 1D perovskite renders an undesired downward band bending for 3D perovskite, resulting in a high hole extraction barrier and reduced hole extraction efficiency. Therefore, rational design and selection of 1D perovskites as the modifiers are essential in balancing defect passivation and hole extraction. In this work, based on simulation calculations, thiocholine iodide (TchI) is selected to prepare 1D perovskite with high work function and then constructs TchPbI 3 /CsPbI 3 1D/3D perovskite heterojunction. Experimental results show that this strategy eliminates the hole extraction barrier at the perovskite/carbon interface, which improves the hole extraction efficiency of corresponding devices. Meanwhile, the strong interaction between the thiol group and Pb suppresses defect-induced recombination effectively and improves the stability of CsPbI 3 . The assembled C-PSCs exhibit a champion efficiency of 19.08% and a certified efficiency of 18.7%. To the best of the knowledge, this is a new efficiency record for inorganic C-PSCs., (© 2024 Wiley‐VCH GmbH.)

Two-dimensional (2D) hybrid organic-inorganic metal halide perovskites offer enhanced stability for perovskite-based applications. Their crystal structure's soft and ionic nature gives rise to strong interaction between charge carriers and ionic rearrangements. Here, we investigate the interaction of photogenerated electrons and ionic polarizations in single-crystal 2D perovskite butylammonium lead iodide (BAPI), varying the inorganic lamellae thickness in the 2D single crystals. We determine the directionality of the transition dipole moments (TDMs) of the relevant phonon modes (in the 0.3-3 THz range) by the angle- and polarization-dependent THz transmission measurements. We find a clear anisotropy of the in-plane photoconductivity, with a ∼10% reduction along the axis parallel with the transition dipole moment of the most strongly coupled phonon. Detailed calculations, based on Feynman polaron theory, indicate that the anisotropy originates from directional electron-phonon interactions.

With the increasing need for reliable storage systems, the conversion-type chemistry typified by bromine cathodes attracts considerable attention due to sizeable theoretical capacity, cost efficiency, and high redox potential. However, the severe loss of active species during operation remains a problem, leading researchers to resort to concentrated halide-containing electrolytes. Here, profiting from the intrinsic halide exchange in perovskite lattices, a novel low-dimensional halide hybrid perovskite cathode, TmdpPb 2 [IBr] 6 , which serves not only as a halogen reservoir for reversible three-electron conversions but also as an effective halogen absorbent by surface Pb dangling bonds, C─H…Br hydrogen bonds, and Pb─I…Br halogen bonds, is proposed. As such, the Zn||TmdpPb 2 [IBr] 6 battery delivers three remarkable discharge voltage plateaus at 1.21 V (I 0 /I - ), 1.47 V (I + /I 0 ), and 1.74 V (Br 0 /Br - ) in a typical halide-free electrolyte; meanwhile, realizing a high capacity of over 336 mAh g -1 at 0.4 A g -1 and high capacity retentions of 88% and 92% after 1000 cycles at 1.2 A g -1 and 4000 cycles at 3.2 A g -1 , respectively, accompanied by a high coulombic efficiency of ≈99%. The work highlights the promising conversion-type cathodes based on metal-halide perovskite materials., (© 2024 The Authors. Advanced Materials published by Wiley‐VCH GmbH.)

The development of lead‐free perovskite photoelectric materials has been an extensive focus in the recent years. Herein, a novel one‐dimensional (1D) lead‐free CsMnCl3(H2O)2 single crystal is reported with solvatochromic photoluminescence properties. Interestingly, after contact with N,N‐dimethylacetamide (DMAC) or N,N‐dimethylformamide (DMF), the crystal structure can transform from 1D CsMnCl3(H2O)2 to 0D Cs3MnCl5 and finally transform into 0D Cs2MnCl4(H2O)2. The solvent‐induced crystal‐to‐crystal phase transformations are accompanied by loss and regaining of water of crystallization, leading to the change of the coordination number of Mn2+. Correspondingly, the luminescence changes from red to bright green and finally back to red emission. By fabricating a test‐paper containing CsMnCl3(H2O)2, DMAC and DMF can be detected quickly with a response time of less than one minute. These results can expand potential applications for low‐dimensional lead‐free perovskites. [ABSTRACT FROM AUTHOR]

The low power conversion efficiency (PCE) of tin‐based perovskite solar cells is mainly caused by severe Sn2+ oxidation and trap state formation. Herein, the reduction of Sn4+ content and trap density is realized through the formation of quasi‐2D tin‐based perovskite by incorporating allylammonium (ALA) cations into formamidinium tin iodide (FASnI3). The composition modification substantially enhances the crystallinity and morphology of the perovskite films, leading to a preferred crystal orientation that facilitates charge carrier transport. After optimization, a high maximum PCE of 9.48% is achieved in a planar p‐i‐n photovoltaic device based on (ALA)2(FA)n−1SnnX3n+1 ( = 25). In the meantime, the device also shows improved stability compared with the FASnI3‐based one. [ABSTRACT FROM AUTHOR]

3D organic–inorganic and all‐inorganic lead halide perovskites have been intensively pursued for resistive switching memories in recent years. Unfortunately, instability and lead toxicity are two foremost challenges for their large‐scale commercial applications. Dimensional reduction and composition engineering are effective means to overcome these challenges. Herein, low‐dimensional inorganic lead‐free Cs3Bi2I9 and CsBi3I10 perovskite‐like films are exploited for resistive switching memory applications. Both devices demonstrate stable switching with ultrahigh on/off ratios (≈106), ultralow operation voltages (as low as 0.12 V), and self‐compliance characteristics. 0D Cs3Bi2I9‐based device shows better retention time and larger reset voltage than the 2D CsBi3I10‐based device. Multilevel resistive switching behavior is also observed by modulating the current compliance, contributing to the device tunability. The resistive switching mechanism is hinged on the formation and rupture of conductive filaments of halide vacancies in the perovskite films, which is correlated with the formation of AgIx layers at the electrode/perovskite interface. This study enriches the library of switching materials with all‐inorganic lead‐free halide perovskites and offers new insights on tuning the operation of solution‐processed memory devices. [ABSTRACT FROM AUTHOR]

1,4‐butanediamine (BEA) is incorporated into FASnI3 (FA=formamidinium) to develop a series of lead‐free low‐dimensional Dion–Jacobson‐phase perovskites, (BEA)FAn−1SnnI3n+1. The broadness of the (BEA)FA2Sn3I10 band gap appears to be influenced by the structural distortion owing to high symmetry. The introduction of BEA ligand stabilizes the low‐dimensional perovskite structure (formation energy ca. 106 j mol−1), which inhibits the oxidation of Sn2+. The compact (BEA)FA2Sn3I10 dominated film enables a weakened carrier localization mechanism with a charge transfer time of only 0.36 ps among the quantum wells, resulting in a carrier diffusion length over 450 nm for electrons and 340 nm for holes, respectively. Solar cell fabrication with (BEA)FA2Sn3I10 delivers a power conversion efficiency (PCE) of 6.43 % with negligible hysteresis. The devices can retain over 90 % of their initial PCE after 1000 h without encapsulation under N2 environment. [ABSTRACT FROM AUTHOR]

The recent rise of low‐dimensional Ruddlesden–Popper (RP) perovskites is notable for superior humidity stability, however they suffer from low power conversion efficiency (PCE). Suitable organic spacer cations with special properties display a critical effect on the performance and stability of perovskite solar cells (PSCs). Herein, a new strategy of designing self‐additive low‐dimensional RP perovskites is first proposed by employing a glycine salt (Gly+) with outstanding additive effect to improve the photovoltaic performance. Due to the strong interaction between CO and Pb2+, the Gly+ can become a nucleation center and be beneficial to uniform and fast growth of the Gly‐based RP perovskites with larger grain sizes, leading to reduced grain boundary and increased carrier transport. As a result, the Gly‐based self‐additive low‐dimensional RP perovskites exhibit remarkable photoelectric properties, yielding the highest PCE of 18.06% for Gly (n = 8) devices and 15.61% for Gly (n = 4) devices with negligible hysteresis. Furthermore, the Gly‐based devices without encapsulation show excellent long‐term stability against humidity, heat, and UV light in comparison to BA‐based low‐dimensional PSCs. This approach provides a feasible design strategy of new‐type low‐dimensional RP perovskites to obtain highly efficient and stable devices for next‐generation photovoltaic applications. [ABSTRACT FROM AUTHOR]

Formamidinium (FA) lead iodide perovskite materials feature promising photovoltaic performances and superior thermal stabilities. However, conversion of the perovskite α‐FAPbI3 phase to the thermodynamically stable yet photovoltaically inactive δ‐FAPbI3 phase compromises the photovoltaic performance. A strategy is presented to address this challenge by using low‐dimensional hybrid perovskite materials comprising guaninium (G) organic spacer layers that act as stabilizers of the three‐dimensional α‐FAPbI3 phase. The underlying mode of interaction at the atomic level is unraveled by means of solid‐state nuclear magnetic resonance spectroscopy, X‐ray crystallography, transmission electron microscopy, molecular dynamics simulations, and DFT calculations. Low‐dimensional‐phase‐containing hybrid FAPbI3 perovskite solar cells are obtained with improved performance and enhanced long‐term stability. [ABSTRACT FROM AUTHOR]

We have obtained a series of low-dimensional hybrid perovskitoids (often referred to as perovskites) based on lead bromide. As organic cations, the derivatives of polyaromatic and conjugated molecules, such as anthracene, pyrene and (E)-stilbene, were chosen to form charge-transfer complexes with various organic acceptors for use as highly tunable components of hybrid perovskite solar cells. X-ray diffraction analysis showed these crystalline materials to be new 1D- and pseudo-layered 0D-perovskitoids with lead bromide octahedra featuring different sharing modes, such as in unusual mini-rods of four face- and edge-shared octahedra. Thanks to the low dimensionality, they can be of use in another type of optoelectronic device, photodetectors.

Over the past decade, lead halide perovskites have emerged as one of the leading photovoltaic materials due to their long carrier lifetimes, high absorption coefficients, high tolerance to defects, and facile processing methods. With a bandgap of ~1.6 eV, lead halide perovskite solar cells have achieved power conversion efficiencies in excess of 25%. Despite this, poor material stability along with lead contamination remains a significant barrier to commercialization. Recently, low-dimensional perovskites, where at least one of the structural dimensions is measured on the nanoscale, have demonstrated significantly higher stabilities, and although their power conversion efficiencies are slightly lower, these materials also open up the possibility of quantum-confinement effects such as carrier multiplication. Furthermore, both bulk perovskites and low-dimensional perovskites have been demonstrated to form hybrids with silicon nanocrystals, where numerous device architectures can be exploited to improve efficiency. In this review, we provide an overview of perovskite solar cells, and report the current progress in nanoscale perovskites, such as low-dimensional perovskites, perovskite quantum dots, and perovskite-nanocrystal hybrid solar cells.

Low-dimensional organic-inorganic hybrid perovskites possess unique microstructural, optical, and electrical properties and offer great application prospects in other fields in addition to optoelectronics. In this study, one-dimensional methylammonium lead iodide (MAPbI 3) nanowires (NWs) were fabricated using an antisolvent-assisted solution method with the addition of phenethylammonium iodide (PEAI). The effects of PEAI on the crystal growth, morphology and microstructure, photoluminescence (PL), and photoresponse performance of the NWs were investigated. The results showed that the addition of the appropriate amount of PEAI transformed the morphology of MAPbI 3 from micron-scale wires to elongated NWs with a high-aspect ratio. Scanning electron microscopy, X-ray diffraction, atomic force microscopy, scanning Kelvin probe microscopy, PL, and time-resolved PL spectroscopic characterizations were conducted, and the results confirmed that PEAI improved the microstructural properties of the as-prepared NWs and manifested surface passivation. The PEAI-treated MAPbI 3 NWs devices also exhibited a superior photoresponsivity as photodetectors compared with the untreated MAPbI 3 microwires devices. This study proposed a simple and effective method that can improve the microstructural and photoelectrical properties of low-dimensional MAPbI 3 crystals, which have a broad application potential for next-generation optoelectronic devices or detectors. • Nanowire-shaped MAPbI 3 with superior microstructural features were fabricated. • A novel approach of adding PEAI was presented to improve MAPbI 3 crystal properties. • PEAI-modified nanowires with larger crystallite size and smaller microstrain were obtained. • Emission and photoresponse properties were improved after PEAI treatment. • PEAI has a remarkable effect on the growth of low-dimensional MAPbI 3 crystals. [ABSTRACT FROM AUTHOR]

Berichtigung: Solvatochromic Photoluminescent Effects in All-Inorganic Manganese(II)-Based Perovskites by Highly Selective Solvent-Induced Crystal-to-Crystal Phase Transformations Lead-free materials, luminescence, manganese, phase transitions, low-dimensional perovskites Keywords: lead-free materials; low-dimensional perovskites; luminescence; manganese; phase transitions EN lead-free materials low-dimensional perovskites luminescence manganese phase transitions 25387 25387 1 11/17/21 20211122 NES 211122 In this Research Article one of the affiliations for the authors Prof. Ziyong Cheng and Prof. Jun Lin was inadvertently omitted. [Extracted from the article]

Keywords: lead-free materials; low-dimensional perovskites; luminescence; manganese; phase transitions EN lead-free materials low-dimensional perovskites luminescence manganese phase transitions 25183 25183 1 11/17/21 20211122 NES 211122 In this Research Article one of the affiliations for the authors Prof. Ziyong Cheng and Prof. Jun Lin was inadvertently omitted. Corrigendum: Solvatochromic Photoluminescent Effects in All-Inorganic Manganese(II)-Based Perovskites by Highly Selective Solvent-Induced Crystal-to-Crystal Phase Transformations Manganese, phase transitions, luminescence, lead-free materials, low-dimensional perovskites. [Extracted from the article]

We have obtained a series of low-dimensional hybrid perovskitoids (often referred to as perovskites) based on lead bromide. As organic cations, the derivatives of polyaromatic and conjugated molecules, such as anthracene, pyrene and (E)-stilbene, were chosen to form charge-transfer complexes with various organic acceptors for use as highly tunable components of hybrid perovskite solar cells. X-ray diffraction analysis showed these crystalline materials to be new 1D- and pseudo-layered 0D-perovskitoids with lead bromide octahedra featuring different sharing modes, such as in unusual mini-rods of four face- and edge-shared octahedra. Thanks to the low dimensionality, they can be of use in another type of optoelectronic device, photodetectors. [ABSTRACT FROM AUTHOR]

Hybrid perovskites are among the most promising materials for optoelectronic applications. Their 2D crystalline form is even more interesting since the alternating inorganic and organic layers naturally forge a multiple quantum-well structure, leading to the formation of stable excitonic resonances. Nevertheless, a controlled modulation of the quantum well width, which is defined by the number of inorganic layers (n) between two organic ones, is not trivial and represents the main synthetic challenge in the field. Here, a conceptually innovative approach to easily tune n in lead iodide perovskite single-crystalline flakes is presented. The judicious use of potassium iodide is found to modulate the supersaturation levels of the precursors solution without being part of the final products. This allows to obtain a fine tuning of the n value. The excellent optical quality of the as synthesized flakes guarantees an in-depth analysis by Fourier-space microscopy, revealing that the excitons orientation can be manipulated by modifying the number of inorganic layers. Excitonic out-of-plane component, indeed, is enhanced when "n" is increased. The combined advances in the synthesis and optical characterization fill in the picture of the exciton behavior in low-dimensional perovskite, paving the way to the design of materials with improved optoelectronic characteristics., (© 2021 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

• Uniform methylammonium lead iodide (MAPbI 3) perovskite nanorods, nanotriangles and nanocubes synthesized using a simple highly controllable and effective ligand-assisted deposition method. • The synthesized MAPbI 3 nanorods not only have extremely small optical band gap (minimum of~1.36 eV), but also have long photoluminescence (PL) lifetime (longest of~7.81 μs) and high absolute PL quantum yields (maximum of ~ 45 %). • The photodetectors based on MAPbI 3 nanorods presented a wide spectral response "window" from 350 to at least 950 nm. • The dramatically improved photo-electric conversion properties of the nanorods photodetectors could be closely related with their morphology dependent properties. [Display omitted] Low-dimensional organic-inorganic hybrid perovskite materials have attracted much attention in photoelectric devices due to their exotic performance in optoelectronics compared with their bulk and thin-film counterparts. In this article, using a simple ligand-assisted deposition method, we successfully synthesized uniform methylammonium lead iodide (MAPbI 3) perovskite nanorods, nanotriangles and nanocubes, and investigated their photoelectric properties after fabricated into photodetectors (PDs) on SiO 2 /Si substrates. It is found that the synthesized MAPbI 3 nanorods not only have extremely small optical band gap (minimum of ~1.36 eV), but also have long photoluminescence (PL) lifetime (longest of ~7.81 μs) and high absolute PL quantum yields (maximum of ~ 45%), and the PL lifetime is more than about one order of magnitude higher than that the reported previously. The PDs based on MAPbI 3 nanorods presented a wide spectral response "window" from 350 to at least 950 nm, and exhibited a photoresponsivity of 12.2 mA/W, a detectivity of 2.67 × 1011 Jones, the on/off ratio of more than 800, the rise/decay time constants of 18/25 ms, under the excitation at 405 nm. Further analysis suggests that the dramatically improved photo-electric conversion properties of the nanorods PDs could be closely related with their morphology dependent properties, including bandgap, PL lifetime, trap density (n trap) and carrier concentration. These results provide a simple and effective method for preparing different morphology low-dimensional MAPbI 3 , and discuss the mechanism of morphology-dependent photoelectric performance of PDs, which is of great significance for potential applications in the field of photoelectronic devices. [ABSTRACT FROM AUTHOR]