Ruddlesden-Popper Research Articles

Empirical Analysis of Stability of An+1BnO3n+1 Ruddlesden–Popper Phases Using Reciprocal n-Values

Layered An+1BnO3n+1 (n = 1…∞) Ruddlesden–Popper (RP) phases are a promising system for a variety of applications. Within the RP family, the thermodynamic properties of the phases are essentially additive with variation in the n value, but at present, there are no general approaches that would allow one to evaluate the individual stability of the RP phases and the possibility of their interconversion. The aim of this paper is to present a novel concept for performing a thermodynamic analysis of RP phases using the reciprocal values of the index n. We present an empirical equation ΔG1/n = ΔGP + B1/n + B2/n2, where ΔG1/n and ΔGP are the molar Gibbs energies of formation of the Ruddlesden–Popper (RP) phase (AO)1/nABO3 and the parent ABO3 perovskite, respectively, and n is a stoichiometry index of An+1BnO3n+1 RP phase. The correlation was validated using available thermodynamic data for the systems Sr-Ti-O, Ca-Ti-O, Sr-Zr-O, La-Ni-O, and La-Co-O. For all A-B combinations, the equation quantitatively describes the Gibbs energy of RP phase formation. Predicted values for the non-linear approximation lie within the experimental uncertainty in determining ΔG1/n. The proposed correlation was used to analyze the relative stability of the RP phases and to determine the feasibility of synthesizing new compounds.

Persistent Exciton Dressed by Weak Polaronic Effect in Rigid and Harmonic Lattice Dion-Jacobson 2D Perovskites.

The emerging two-dimensional (2D) Dion-Jacobson (DJ) perovskites with bidentate ligands have attracted significant attention due to enhanced structural stability compared with conventional Ruddlesden-Popper (RP) perovskites with monodentate ligands linked by van der Waals interactions. However, how the pure chemical bond lattice interacts with excited state excitons and its impact on the exciton nature and dynamics in 2D DJ-perovskites, particularly in comparison to RP-perovskites, remains unexplored. Herein, by a combined spectroscopy study on excitonic and structural dynamics, we reveal a persistent exciton dressed by a weak polaronic effect in DJ-perovskite due to their rigid and harmonic lattice, in striking contrast to significantly screened exciton polaron observed in RP-perovskites. Despite the similar exciton binding energy (∼0.3 eV) in both n = 1 DJ- and RP-perovskites with near-identical crystal structure, photoexcitation results in a slightly screened exciton with minimal structural relaxation and a retained binding energy of ∼0.29 eV in DJ-perovskites but strongly screened exciton polaron with a binding energy of ∼0.13 eV in RP-perovskites. Structural dynamics further highlight the rigid and harmonic lattice motion in DJ-perovskites, as opposed to the thermally activated anharmonic lattice in RP-perovskites, arising from their distinct bonding modes. Our study offers insights into modulating excited state properties in 2D perovskites, simulating the rational design of hybrid semiconductors with tailored properties and functionalities.

Controlled Growth of 2D‐3D Perovskite Lateral Heterostructures for Wavelength‐Tunable Light Communication

AbstractLateral heterostructures based on halide perovskites exhibit great potential in the advancement of next‐generation optoelectronic devices. Among them, mixed dimensional perovskite heterostructures, particularly 2D‐3D ones, offer promising opportunities for semiconductor integration and device miniaturization by combining the advantages of 2D and 3D perovskites. However, the controllable and rapid growth of 2D‐3D halide perovskite lateral heterostructures has not yet been achieved. This study presents an efficient strategy that integrates one‐pot method and space‐confined process to enable liquid‐phase lateral growth of a series of 2D Ruddlesden‐Popper (RP) perovskites on the sides of 3D perovskites. The photodetectors (PDs) based on (BA)2MAn‐1PbnBr3n+1‐MAPbBr3 (n = 1, 2, 3) lateral heterostructures demonstrate outstanding optoelectronic performance, featuring an on/off ratio of up to 1.4 × 104, a high responsivity of 4.4 A W−1 and a detectivity of 3.9 × 1013 Jones at 425 nm, 3 V bias. In addition, by combining the tunable dual‐band photoresponse characteristic with the dual‐beam irradiation modes, a wavelength‐tunable light communication system based on the lateral heterostructure PDs is realized. This work provides a convenient and reliable approach for the direct growth of mixed‐dimensional halide perovskite heterostructures, further demonstrating their potential in high‐performance detecting and dual‐band sensing fields.

Multi-Noncentrosymmetric Polar Order in 2D Hybrid Lead Chloride with Broadband Emission and High-Temperature Second-Harmonic Generation Switching.

Two-dimensional lead halide perovskites represent a fascinating class of hybrid semiconductors for solar cell, light-emitting, nonlinear optical (NLO), and ferroelectric applications. A notable subset within this category is luminescent ferroelectrics, which have garnered considerable attention for their potential in integrated photoelectronic devices. In this study, we employed an organic amine halogenation strategy (also referred to as halogen engineering), which is renowned for its efficacy in inducing polar order through crystal engineering. Consequently, we synthesized a layered Ruddlesden-Popper (RP) lead chloride comprising 3-chloropropylammonium cations (CPA+), with the chemical formula CPA2PbCl4. This compound features as many as four temperature-dependent crystal phases, with phase transitions observed at T1 = 353.1 K (343.9 K), T2 = 211.7 K (208.6 K), and T3 = 182.0 K (178.2 K) in the heating (cooling) cycles. Employing a multitechnique approach─including thermal analysis, X-ray diffraction, dielectric and pyroelectric current measurements, Raman spectroscopy, and second-harmonic generation (SHG) studies─we determined the mechanisms of the structural phase transitions. Our findings demonstrate polar order of phase II (space group Cmc21), phase III (space group Pna21), and phase IV (space group Pca21), while also confirming the centrosymmetric nature of phase I (space group Cmce). X-ray diffraction data revealed that the I to II PT is of a ferroelectric nature, devoid of ferroelastic strain, a conclusion further supported by pyroelectric measurements. CPA2PbCl4 features negative linear thermal expansion and broadband emission, which transitions to white light above 180 K. Remarkably, CPA2PbCl4 also demonstrates high-temperature SHG on-off switching with a high contrast ratio of 300:1 along with good switching stability, as evidenced by SHG cycling studies at heating/cooling rates ranging from 5 to 50 K/min. This SHG study also sets new standards for the field of SHG switching by providing a method to quantify the thermal responsiveness of SHG-switchable materials using the treq (time requirement) parameter. Overall, our findings show that the halogenation strategy has led to the discovery of a rare example of an RP perovskite exhibiting coexistence of white-light emission, SHG on-off thermal bistability, ferroelectricity, and negative linear thermal expansion.

Tailored Polymer Hole-Transporting Materials with Multisite Passivation Functions for Effective Buried-Interface Engineering of Inverted Quasi-2D Perovskite Solar Cells.

Although quasi-2D Ruddlesden‒Popper (RP) perovskite exhibits advantages in stability, their photovoltaic performance are still inferior to 3D counterparts. Optimizing the buried interface of RP perovskite and suppress energetic losses can be a promising approach for enhancing efficiency and stability of inverted quasi-2D RP perovskite solar cells (PSCs). Among which, constructing polymer hole-transporting materials (HTMs) with defect passivation functions is of great significance for buried-interface engineering of inverted quasi-2D RP PSCs. Herein, by employing side-chain tailoring strategy to extend the π-conjugation and regulate functionality of side-chain groups, target polymer HTMs (PVCz-ThSMeTPA and PVCz-ThOMeTPA) with high mobility and multisite passivation functions are achieved. The presence of more sulfur atom-containing groups in side-chain endows PVCz-ThSMeTPA with increased intra/intermolecular interaction, appropriate energy level, and enhanced buried interfacial interactions with quasi-2D RP perovskite. The hole mobility of PVCz-ThSMeTPA is up to 9.20×10-4 cm2 V-1 S-1. Furthermore, PVCz-ThSMeTPA as multifunctional polymer HTM with multiple chemical anchor sites for buried-interface engineering of quasi-2D PSCs can enable effective charge extraction, defects passivation, and perovskite crystallization modulation. Eventually, the PVCz-ThSMeTPA-based inverted quasi-2D PSC achieves a champion power conversion efficiency of 22.37%, which represents one of the highest power conversion efficiencies reported to date for quasi-2D RP PSCs.

Structure and Magnetic Properties of the n = 3 Ruddlesden-Popper Oxyfluoride La0.5Sr3.5Fe3O7.5F2.6.

Ruddlesden-Popper (RP) compounds of the general formula (AX)(ABX3)n with their unique sequence of perovskite-like (ABX3) and rock-salt-like units (AX) promise applications in diverse fields such as catalysis and superconductivity. Fluorination of RP oxides often leads to dramatic changes in the material properties, caused by differences in the atomic and electronic structure. While current research focuses on fluorination of n = 1 type RP oxides (A2BO4), n = 3 RP oxyfluorides have remained elusive. We present the synthesis of the first iron-based n = 3 RP oxyfluoride, La0.5Sr3.5Fe3O7.5F2.6, which was obtained from an oxide precursor by topochemical fluorination with poly(vinylidene fluoride). Joint Rietveld refinements of neutron and powder X-ray diffraction data were used to determine the crystal structure. Best results were obtained in the space group Pbca (No. 61) with a = 5.5374(1) Å, b = 5.5441(1) Å, and c = 29.2541(2) Å. The effect of the aliovalent incorporation of fluoride ions is particularly evident with respect to changes in structure and magnetic properties. The magnetic behavior was studied using field- and temperature-dependent magnetization measurements, Mößbauer spectroscopy, and neutron diffraction. Additional magnetic Bragg reflections observed in the room-temperature neutron data were successfully refined in the space group Pbca (61.1.497 in Opechowski-Guccione notation), indicating a G-type antiferromagnetic ordering with a surprisingly high Néel temperature above 300 K. This strong increase of TN by several hundred Kelvin compared to the parent oxide is particularly remarkable.

High-entropy design of Ruddlesden-Popper structured LNO for enhanced performance in proton solid oxide fuel cells

Protionic Ceramic Fuel Cells (PCFCs) are devices that efficiently convert chemical energy to electrical energy at low temperatures. Significant research efforts have been directed towards the development of cathodes with enhanced catalytic activity. In this work, a high-entropy approach was employed at the A site of La2NiO4+δ (LNO) with a Ruddlesden-Popper (R-P) structure, resulting in the synthesis of the LaPr0.2Sm0.2Ba0.2Sr0.2Ca0.2NiO4+δ (HE-LPSBSCN) cathode. A comprehensive series of tests demonstrated that this high-entropy strategy improved the oxygen reduction reaction (ORR) activity, hydration behavior, well operational stability, and electronic conductivity of LNO. The HE-LPSBSCN cathode demonstrated record-breaking performance, achieving a maximum power density of 2004 mW cm−2 at 700 °C. This finding provides novel insights for the rational design and optimization of highly catalytically active cathodes for PCFCs.

Efficient Perovskite Light Emitting Diodes Enabled by Mixed Ruddlesden–Popper (RP) Perovskite–Perovskite Planar Heterojunction between Hole Transport and Emission Layers

Efficient Perovskite Light Emitting Diodes Enabled by Mixed Ruddlesden–Popper (RP) Perovskite–Perovskite Planar Heterojunction between Hole Transport and Emission Layers

Bulk high-temperature superconductivity in pressurized tetragonal La2PrNi2O7.

The Ruddlesden-Popper (R-P) bilayer nickelate, La3Ni2O7, was recently found to show signatures of high-temperature superconductivity (HTSC) at pressures above 14 GPa (ref. 1). Subsequent investigations achieved zero resistance in single-crystalline and polycrystalline samples under hydrostatic pressure conditions2-4. Yet, obvious diamagnetic signals, the other hallmark of superconductors, are still lacking owing to the filamentary nature with low superconducting volume fraction2,4,5. The presence of a new 1313 polymorph and competing R-P phases obscured proper identification of the phase for HTSC6-9. Thus, achieving bulk HTSC and identifying the phase at play are the most prominent tasks. Here we address these issues in the praseodymium (Pr)-doped La2PrNi2O7 polycrystalline samples. We find that substitutions of Pr for La effectively inhibit the intergrowth of different R-P phases, resulting in a nearly pure bilayer structure. For La2PrNi2O7, pressure-induced orthorhombic to tetragonal structural transition takes place at Pc ≈ 11 GPa, above which HTSC emerges gradually on further compression. The superconducting transition temperatures at 18-20 GPa reach and , which are the highest values, to our knowledge, among known nickelate superconductors. Importantly, bulk HTSC was testified by detecting clear diamagnetic signals below about 75 K with appreciable superconducting shielding volume fractions at a pressure of above 15 GPa. Our results not only resolve the existing controversies but also provide directions for exploring bulk HTSC in the bilayer nickelates.

Simulation of diffraction patterns for Ruddlesden–Popper (RP) tetragonal structures with RP faults

A theoretical analysis of diffraction patterns was performed for two representatives of layered perovskite-type tetragonal phases of the Ruddlesden–Popper series (RP) with the general formula A n+1 B n O3n+1 (n = 1, 2), which contain RP faults (layer alternation defects) in a wide range of concentrations. The results of theoretical calculations can be used in the future for correct interpretation of X-ray powder diffraction experimental data and for quantitative estimation of the deviation from stoichiometry and structural perfection of this type of compound.

Electronic structure regulation of Cu-based Ruddlesden-Popper perovskites by cobalt doping for enhanced degradation of oilfield fracturing wastewater in electrocatalytic peroxymonosulfate system

Purification of oilfield fracturing wastewater is the most challenging type of oilfield wastewater treatment. In this work, a heterogeneous electrocatalytic peroxymonosulfate (PMS) system was established to treat oilfield wastewater using Co-doping induced Cu-based Ruddlesden-Popper (RP) perovskites as catalysts. Characterization results illustrated that the obtained catalysts were generated the heterojunction of LaCoO3/La2CuO4 and the Co would transfer electrons to Cu, resulting in a higher chemical oxygen demand (COD) degradation efficiency (> 80 %) of oilfield fracturing wastewater under the neutral environment. Singlet oxygen (1O2) played the main function for COD removal with analysis results of reactive oxygen species (ROS). Experimental results and theoretical calculations indicated that the reduction effect of carbon felt (GF) cathode and the redox cycle of Cu(I)/Cu(II) and Co(II)/Co(III) accelerated the activation of PMS. Moreover, the lattice oxygen participated in the generation of ROS. Significantly, the LaCoO3/La2CuO4 heterojunction displayed a higher total density of states (TDOS) value near the Fermi level, implying their favorable electron transfer for PMS activation. This study opens new avenue for resolving the challenge of oilfield fracturing wastewater pollution.

Deterministic Synthesis of a Two-Dimensional MAPbI3 Nanosheet and Twisted Structure with Moiré Superlattice.

The synthesis of extremely thin 2D halide perovskites and the exploration of their interlayer interactions have garnered significant attention in current research. A recent advancement we have made involves the development of a successful technique for generating ultrathin MAPbI3 nanosheets with controlled thickness and an exposed intrinsic surface. This innovative method relies on utilizing the Ruddlesden-Popper (RP) phase perovskite (BA2MAn-1PbnI3n+1) as a template. However, the precise reaction mechanism remains incompletely understood. In this work, we systematically examined the dynamic evolution of the phase conversion process, with a specific focus on the influence of inorganic slab (composed of [PbI6]4- octahedrons) numbers on regulating the thickness and quality of the resulting MAPbI3 nanosheets. Additionally, the atomic structure is directly visualized using the transmission electron microscopy (TEM) method, confirming its exceptional quality. To illustrate interfacial interactions in ultrathin structures, artificial moiré superlattices are constructed through a physical transfer approach, revealing multiple localized high-symmetry stacks within a distinctive square moiré pattern. These findings establish a novel framework for investigating the physics of interfacial interactions in ionic semiconducting crystals.

Enhancing perovskite solar cell efficiency to 28.17% by Integrating Dion-Jacobson 2D and 3D phase perovskite Absorbers

Efficiency of power conversion for both kinds of inorganic as well as organic perovskites-based cells has increased in the last few years. To overcome this stability-related issue of 3D perovskite cells,2D perovskite has become an alternative option.The structure and the device, both are destabilized by the weak interactions observed in between the layers of the layered perovskite since the Ruddlesden Popper (RP) phase of 2D perovskite has a weak Van der Waal gap present in between the monoammonium cation layer.The PCE of perovskite cells has risen to 25 %. Commercialization of perovskites on a large scale as solar is a challenging task because lead is toxic.Keeping the toxic property of lead in mind we have used FTO (window layer)/TiO2(ETL)/(PDA)(MA)n-1PbnI3n+1(absorber layer)/Csx(FA0.4MA0.6)1-xPbI2.8Br0.2(absorber layer)/ spiro-OMeTAD (HTL).It has been observed that the DJ and RP phases of 2D PSC are individually found much more stable than their 3D counterpart used for perovskite-based solar cells. DJ and RP are merged to become proof of the efficiency as well as environmental stability of 2D perovskite-based solar cells.Several material parameters that affect the performance result obtained from the device,like the electron transport layer(ETL), hole transport layer(HTL), the thickness of the absorbing layer,etc were considered,studied,and also have been optimized.

Defect Structure, Oxygen Ion Conduction, and Conducting Mechanism in Ruddlesden-Popper Sr3Zr2-xMxO7-0.5x (M = Ga, Y, In).

Ruddlesden-Popper (RP)-structured materials based on transition metals with a variable valence, such as Fe, Mn, Ni, and so on, have been well documented for their potential of being used as electrodes in solid-oxide fuel cells. However, RP materials with pure or dominant ionic conduction are rare. Here, a series of Zr-based RP materials Sr3Zr2-xMxO7-0.5x (M = Ga, Y, In) with electrical conductivity as high as 3.25 × 10-3 S cm-1 at 900 °C in air was reported, which represents the highest conductivity for the Zr-based RP materials and is comparable to that of the recently reported In-based RP oxide-ion conductors, such as NdBaInO4-based and La2BaIn2O7-based materials. Under low oxygen partial pressure (pO2), the doped samples show pure ionic conducting behaviors without n-type electronic conductivity. The defect formation energies, local structure around the oxygen vacancies, and oxide-ion-conducting mechanism of the acceptor-doped Sr3Zr2O7-based materials were studied for the first time. The results revealed a two-dimensional oxide ion migration characteristic within the perovskite slabs. This work therefore provides a good reference for developing new oxide-ion conductors in the Zr-based RP-structured materials.

Highly Sensitive Two‐Dimensional Ruddlesden‐Popper Perovskites for Thermochromic Smart Windows

AbstractWith the growing demand for high‐performance smart windows, the discover of a class of thermochromic materials with reversible cycling and rapid response characteristics has become urgent. In this work, we have uncovered a two‐dimensional (2D) Ruddlesden‐Popper (RP) phase halide perovskite, (PMA)2MAPb2I7−xClx, where PMA=C6H5CH2NH3 and MA=CH3NH3, exhibiting exceptional reversible thermochromic properties. The 2D RP phase perovskite thin film features a low transition temperature (Tc=30 °C from the hydrated state to the hot state, along with a fast transition time of 40 s. Furthermore, the addition of 0.5 times excess MAI significantly enhances the visible light transmittance of the hydrated state. Characteristic hydration peaks in X‐ray diffraction patterns and O−H bond absorption peaks Fourier‐transform infrared spectra are observed in the thin film in its hydrated state, which disappear in the hot state, validating its reversible thermochromic properties. Additionally, a solar cell based on the thermochromic 2D RP phase thin film achieves a power conversion efficiency of 2.31 %, offering a promising solution for advanced smart window technologies.

Opto-electrical study of 4T perovskite-chalcogenide tandem solar cell with the addition of quasi-2D perovskite as capping layer of 3D perovskite layer

This study presents a four-terminal (4T) perovskite-chalcogenide tandem solar cell (TSC) that includes quasi-2D perovskite material in the top sub-cell in order to provide a stable structure, and the bottom sub-cell contains Zn(O,S,OH) material to provide a nontoxic buffer layer. First, a reference TSC with a total power conversion efficiency (PCE) of 26.48% is modeled, using MAPbI3 and CIGSSe as 3D perovskite and chalcogenide absorber layers (ALs), respectively. Next, two structures are designed to produce a stable SC using the Ruddlesden Popper (RP) quasi-2D perovskite materials, which have the chemical formula BA2MAm−1PbmI3m+1, m = 2–5. The initial structure uses quasi-2D perovskites in place of the 3D perovskite AL. According to the results, BA2MAPb2I7 represents the maximum PCE of 16.00%, 10.48% less than previously. This is caused by quasi-2D materials’ high Eg and low carrier mobility. In the second structure, 3D perovskite AL is capped with the quasi-2D perovskites. In terms of attaining maximum PCE, the optimal TSC is found for BA2MA3Pb4I13 with a PCE of 25.80%. Compared to the initial structure, this one’s PCE increased by 61.25%. In order to boost PCE, a 80 nm-thick anti-reflection (AR) layer is added to the second structure, and the PCE increased to 27.48%. Therefore, the final TSC is proposed as a 4T quasi-2D/3D perovskite-chalcogenide TSC that is stable, and has nontoxic buffer layer, with 3.78% more PCE than the reference structure.

Deciphering Structure and Charge Carrier Behavior in Reduced‐Dimensional Perovskites

AbstractReduced‐dimensional perovskites (RDPs) have advanced perovskite optoelectronic devices due to their tunable energy landscape, structure, and orientation. However, the origin of structural and photophysical property changes when moving from low‐dimensional to high‐dimensional RDPs remains to be understood. This study systematically reveals structural and photophysical properties of slot‐die‐coated Dion‐Jacobson (DJ) and Ruddlesden‐Popper (RP) RDPs with different dimensionalities. RP RDPs with lower dimensionality (n = 2) exhibit a dominant n = 2 phase, preferential out‐of‐plane orientation, and longer charge carrier lifetime compared with DJ RDPs. In addition, the formation kinetics of RDPs with higher dimensionality (n = 4) are unraveled by in situ X‐ray scattering, showing the favorable formation of the lower‐n phase in RP RDPs. The formation of these lower‐n phases is thermodynamically and stoichiometrically favored, while these phases are likely in the form of an “intermediate phase” which bridges the 3D‐like and lower‐n phases in DJ RDPs. DJ RDPs with higher dimensionality demonstrate comparable phase purity, preferential orientation, spatially vertical phase homogeneity, and longer charge carrier lifetime. As such, DJ‐based perovskite solar cells (PSCs) (n = 4) demonstrate better photostability under operational conditions than RP‐based PSCs. Thus, the work paves the way for the utilization of RDPs to upscale PSCs.

Vapor Growth of All-Inorganic 2D Ruddlesden-Popper Lead- and Tin-Based Perovskites.

The 2D Ruddlesden-Popper (RP) perovskites Cs2PbI2Cl2 (Pb-based, n = 1) and Cs2SnI2Cl2 (Sn-based, n = 1) stand out as unique and rare instances of entirely inorganic constituents within the more expansive category of organic/inorganic 2D perovskites. These materials have recently garnered significant attention for their strong UV-light responsiveness, exceptional thermal stability, and theoretically predicted ultrahigh carrier mobility. In this study, we synthesized Pb and Sn-based n = 1 2D RP perovskite films covering millimeter-scale areas for the first time, utilizing a one-step chemical vapor deposition (CVD) method under atmospheric conditions. These films feature perovskite layers oriented horizontally relative to the substrate. Multilayered Cs3Pb2I3Cl4 (Pb-based, n = 2) and Cs3Sn2I3Cl4 (Sn-based, n = 2) films were also obtained for the first time, and their crystallographic structures were refined by combining X-ray diffraction (XRD) and density functional theory (DFT) calculations. DFT calculations and experimental optical spectroscopy support band-gap energy shifts related to the perovskite layer thickness. We demonstrate bias-free photodetectors using the Sn-based, n = 1 perovskite with reproducible photocurrent and a fast 84 ms response time. The present work not only demonstrates the growth of high-quality all-inorganic multilayered 2D perovskites via the CVD method but also suggests their potential as promising candidates for future optoelectronic applications.

Layer-dependent transport and optoelectronic properties in 2D all-inorganic Ruddlesden–Popper perovskite Cs2PbBr4

In recent years, two-dimensional (2D) all-inorganic Ruddlesden–Popper (RP) perovskites have attracted significant research attention. In this study, the electronic and carrier transport properties of 2D layered RP perovskite Cs2PbBr4 are studied by DFT calculations. The carrier mobility of the RP perovskite Cs2PbBr4 layers are studied based on deformation-potential (DP) theory. We found that the carrier mobility in 2D Cs2PbBr4 layers are enhanced as the number of layers increases. For trilayer Cs2PbBr4 the electron mobility reaches 7588.7 cm2V−1s−1, which is much higher than the widely studied bulk MAPbI3 (1500 cm2V−1s−1). In addition, the exciton binding energies are also calculated. Our work proves that the 2D RP perovskite Cs2PbBr4 layers are potential candidates for the photoelectronic devices applications.

Deciphering the Interplay of Structure and Charge Carrier Dynamics in Reduced-Dimensional Perovskites

Reduced-dimensional perovskites (RDPs) have advanced the development of perovskite solar cells (PSCs) due to their tunable energy landscape, structure, and orientation. Thus, we aim for an increase in the understanding of structure-photophysical properties of Dion-Jacobson (DJ) and Ruddlesden-Popper (RP) RDPs with different dimensionalities. Our findings reveal that RP RDPs with lower dimensionality exhibits a dominant n=2 phase, preferential out-of-plane orientation, and longer charge carrier lifetime compared with DJ RDPs, as evidenced by X-ray scattering technique and transient absorption spectroscopy. In addition, we unveil the film growth of respective RDPs by in-situ X-ray scattering, showing the stoichiometry-determined phase growth. The formation of lower-n phases in RP RDPs with higher dimensionality is thermodynamically favored, while those phases are likely in the form of “intermediate phase”, which bridge the 3d-like and lower-n phases in DJ RDPs. DJ RDPs with higher dimensionality demonstrate comparable phase purity, giving rise to more sufficient energy transfer and longer charge carrier lifetime. As such, DJ-based PSCs (n=4) demonstrate better device stability under ISOS-I-L conditions compared to RP-based PSCs. Leveraging these structural and photophysical insights, our work paves the way for dictating the utilization of RDPs in 3D PSCs and the fabrication of quasi-2D solar cells.