Dion-Jacobson Phase Research Articles

Effect of alkali-metal cations on synthesis of stoichiometric layered perovskite oxynitrides

Layered perovskite oxynitrides, which contain a stoichiometric lattice N content, are promising visible-light-driven photocatalysts. However, their synthesis remains a challenge for inorganic chemists. Herein, we report the successful synthesis of layered perovskite oxynitrides A2A'2Ta3O9N with different cations at A/A′-sites (A = Na, K, Rb, Cs; A' = Ca, Sr, Ba) via thermal ammonolysis from layered Dion–Jacobson phase oxide precursors (AA'2Ta3O10). We present the first experimental study of layered oxynitride formation across the A and A′ cation size series, revealing that the A-site alkali-metal cation rather than the A′-site alkaline-earth metal cation is critical to the successful synthesis of the stoichiometric layered oxynitrides. Nitrided products with A = Na, K, or Rb exhibited structural transitions, while no structural transition was observed for Cs. Interestingly, nitrided products with A = Rb and K exhibited the same structural transition behavior, i.e., alkali-metal cations entered the interlayer to form an oxynitride with a composition A2A'2Ta3O9N·nH2O. By contrast, with A = Na, it formed an oxynitride that differs from the Ruddlesden–Popper structure but has the same composition of A2A'2Ta3O9N·nH2O. Our finding suggests that, as the cation size decreases from Cs to Na, stoichiometric A2A'2Ta3O9N compositions become more favorable than compounds with A-sites. This work provides a new perspective for the future design and synthesis of novel layered oxynitrides.

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

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

Chemical Behavior and Local Structure of the Ruddlesden-Popper and Dion-Jacobson Alloyed Pb/Sn Bromide 2D Perovskites.

The alloyed lead/tin (Pb/Sn) halide perovskites have gained significant attention in the development of tandem solar cells and other optoelectronic devices due to their widely tunable absorption edge. To gain a better understanding of the intriguing properties of Pb/Sn perovskites, such as their anomalous bandgap's dependence on stoichiometry, it is important to deepen the understanding of their chemical behavior and local structure. Herein, we investigate a series of two-dimensional Ruddlesden-Popper (RP) and Dion-Jacobson (DJ) phase alloyed Pb/Sn bromide perovskites using butylammonium (BA) and 3-(aminomethyl)pyridinium (3AMPY) as the spacer cations: (BA)2(MA)n-1PbxSnn-xBr3n+1 (n = 1-3) and (3AMPY)(MA)n-1PbxSnn-xBr3n+1 (n = 1-3) through a solution-based approach. Our results show that the ratio and site preference of Pb/Sn atoms are influenced by the layer thickness (n) and spacer cations (A'), as determined by single-crystal X-ray diffraction. Solid-state 1H, 119Sn, and 207Pb NMR spectroscopy analysis shows that the Pb atoms prefer the outer layers in n = 3 members: (BA)2(MA)PbxSnn-xBr10 and (3AMPY)(MA)PbxSnn-xBr10. Layered 2D DJ alloyed Pb/Sn bromide perovskites (3AMPY)(MA)n-1PbxSnn-xBr3n+1 (n = 1-3) demonstrate much narrower optical band gaps, lower energy PL emission peaks, and longer carrier lifetimes compared to those of RP analogs. Density functional theory calculations suggest that Pb-rich alloys (Pb:Sn ∼4:1) for n = 1 compounds are thermodynamically favored over 50:50 (Pb:Sn ∼1:1) compositions. From grazing-incidence wide-angle X-ray scattering (GIWAXS), we see that films in the RP phase orient parallel to the substrate, whereas for DJ cases, random orientations are observed relative to the substrate.

Harnessing the potential of Dion-Jacobson perovskite solar cells: Insights from SCAPS simulation techniques

Although perovskite solar cells (PSCs) have shown considerable advancement in recent years, their extensive usage is hindered by the major challenge of ensuring long-term stability. However, the enhanced stability of 2D-structure Dion-Jacobson (DJ) phase halide perovskites makes them a promising alternative to the traditional 3D perovskites, suggesting potential for broader application. In this numerical simulation, bulky organic ammonium spacer pentamethylenediamine (PeDA) was incorporated into DJ perovskite films with four different layer numbers (n = 3, 4, 5, and 6), which correspond to PeDAMA2Pb3I10, PeDAMA3Pb4I13, PeDAMA4Pb5I16, and PeDAMA5Pb6I19, respectively. Various parameters were adjusted to assess their impact on device performance. A current density–voltage (J-V) characterization was conducted for each value of n to compare their efficiencies. The number of layers was found to significantly influence efficiency, with the highest performance achieved at n = 6, resulting in an open-circuit voltage (VOC) of 1.27 V, a short-circuit current density (JSC) of 22.83 mA/cm2, a power conversion efficiency (PCE) of 21.17%, and a fill factor (FF) of 72.72%. These results demonstrate the potential of DJ perovskite solar cells with PeDA spacers as stable and efficient alternatives for photovoltaic applications.

Mixed Ruddlesden–Popper and Dion–Jacobson Phase Perovskites for Stable and Efficient Blue Perovskite LEDs

AbstractProducing efficient blue and deep blue perovskite LEDs (PeLEDs) still represents a significant challenge in optoelectronics. Blue PeLEDs still have problems relating to color, luminance, and structural and electrical stability so new materials are needed to achieve better performance. Recent reports suggest using low n states (n = 1, 2, 3) to achieve blue electroluminescence in Ruddlesden–Popper (RP) perovskite films. However, there are fewer reports on the other quasi‐2D structure, Dion–Jacobson (DJ) perovksites, despite their highly desirable optical properties, due to the difficulty in achieving charge injection. To resolve this issue, herein, w e have mixed DJ phase precursors, propane‐1,3‐diammonium (PDA) bromide into RP phase perovskites and fabricated low‐dimensional PeLEDs. It is found that these specific precursors aid in suppressing both the low n (n = 1) and high n (n ≥ 4) quasi‐2D RP phases and is an effective strategy in blue‐shifting sky‐blue RP perovskites into the sub‐470 nm region. With optimization of the PDA concentration and device layers, it is achieved an external quantum efficiency of 1.5% at 469 nm and stable electroluminescence for the first deep blue PeLED to be reported using DJ perovskites.

Centimeter-Sized Single Crystals of Dion-Jacobson Phase Lead-Free Double Perovskite for Efficient X-ray Detection.

2D Dion-Jacobson (DJ) phase hybrid perovskites have shown great promise in the photoelectronic field owing to their outstanding optoelectronic performance and superior structural rigidity. However, DJ phase lead-free double perovskites are still a virgin land with direct X-ray detection. Herein,wehave designed and synthesized a new DJ phase lead-free layered double perovskite of (HIS)2 AgSbBr8 (1, HIS2+ = histammonium). Centimeter-sized (18 × 10 × 5 mm3 ) single crystals of 1 are successfully grown via the temperature cooling technique, exhibiting remarkable semiconductive characteristics such as a high resistivity (2.2 × 1011 Ω cm), a low trap state density (3.56 × 1010 cm-3 ), and a large mobility-lifetime product (1.72 × 10-3 cm2 V-1 ). Strikingly, its single-crystal-based X-ray detector shows a high sensitivity of 223 µC Gy-1 air cm-2 under 33.3V mm-1 , a low detection limit (84.2 nGyair s-1 ) and superior anti-fatigue. As far asweknow,wefirstly demonstrates the potential of 2D DJ phase lead-free hybrid double perovskite in X-ray detection, showing excellent photoelectric response and operational stability. This work will pave a promising pathway to the innovative application of hybrid perovskites for eco-friendly and efficient X-ray detection.

Prominent Free Charges Tunneling Through Organic Interlayer of 2D Perovskites.

The diversity of organic cations greatly enriches the species of 2D perovskites; traditional 2D Ruddlesden-Popper (RP) and Dion-Jacobson (DJ) perovskites are synthesized by two different organic amines. Here, according to the difference in pKa values between conjugated acids of monoprotonated and biprotonated 4-(2-Aminoethyl)pyridine (4AEPy) ions, the 2D perovskites of RP (4AEPy)2 PbI4 and DJ (4AEPy)PbI4 from same organic amine is reported, which can realize reversible transformation under the treatment of HI and NH3 , respectively. The interaction of N-H···N hydrogen bond between adjacent organic molecules in (4AEPy)2 PbI4 leads to the bending conformation of ethylamine groups, which results in a 2.4 Å reduction in layer spacing compared to typical phenylethylamine lead iodine ((PEA)2 PbI4 ) 2D perovskite. Besides, the ethylamine groups of organic layers in (4AEPy)PbI4 are deeply inserted into octahedral cavities and directly participate in the construction of the conduction band minimum, which leads to a small exciton binding energy of 27.3 meVtogeneratefreecharges. The stronger coupling between the organic and inorganic layers and the minor exciton binding energy can promote the DJ phase to possess a more stable structure and better optoelectronic properties. Thusthe (4AEPy)PbI4 device displays better light response and X-ray detection capability with a high sensitivity of 5627 µC Gyair -1 cm-2 and the lowest detectable dose rate of 20 nGyair s-1 .

Managing Interfacial Hot‐Carrier Cooling and Extraction Kinetics for Inverted Ma‐Free Perovskite Solar Cells Over 23% Efficiency via Dion–Jacobson 2D Capping Layer

AbstractWhile quasi‐2D perovskite is often used in inverted perovskite solar cells (PSCs) to improve the interfacial carrier transfer, the development of pure 2D perovskite with superior stability is rarely seen and the corresponding carrier‐extraction kinetics remains unclear. Here, a variety of hexatomic ring cations including piperidine, pyridine, and cyclohexane are introduced to modify the perovskite/electron transport layer interface. The Dion–Jacobson phase 2D cladding (n = 1) based on 3‐(aminomethyl) piperidinium is proved to form a coordinated energy landscape and homogeneous surface potential distribution, and effectively prolong the electron diffusion length (≈1.58 µm) and accelerate the hot‐carrier extraction rate (2.5 times that of Control at 400 K). Furthermore, the quasi‐2D treatment (n ≈ 3,4) demonstrated a slight escalation in short‐circuit current, but failed to inhibit the interdiffusion of Ag, Pb, and I under illumination. Finally, one of the state‐of‐art power conversion efficiency (PCE) for MA‐free inverted PSCs is achieved at 23.62% with increased open‐circuit voltage (≈1.15 V) and fill factor (≈82.8%). Most importantly, 89% and 93.6% of initial PCE are retained after 720 h under 85 °C heating and 1000 h under maximum power point tracking, illustrating satisfactory thermal and operational stability with pure 2D perovskite capping layer.

Green-antisolvent-induced homogeneous phase distribution for efficient and stable MA-free 2D perovskite solar cells

The phase distribution of two-dimensional (2D) perovskites is critical for solar cell power conversion efficiency (PCE). Here, we report a simple green anti-solvent (ethyl acetate, EA) method for obtaining uniform phase dispersion of methylamine (MA)-free quasi-2D Dion-Jacobson (DJ) phase perovskite films (DMePDA)FA3Pb4I13 (n = 4). The films present a more homogeneous phase distribution for their rapid extraction of solvents and the interaction between Pb2+ and the carbonyl group in EA, resulting in a more shining surface, reduced surface-defect density, higher out-plane mobility, and higher conductivity. We obtain a PCE of 18.86 %, which is the highest for MA-free DJ phase 2D perovskite-based devices. In addition, the target devices maintain 85 % and 90 % of their initial values after 1008 h under 85 % relative humidity at 85 ℃ (ISOS-D-3) and continuous illumination at maximum power point (MPP) tracking at ∼ 45 ℃ (ISOS-L-1), respectively.

Layer-number tailoring and template-induced orientation control of 2D perovskites on 3D perovskites by adopting the Dion–Jacobson phase

Orientation-controlled 2D perovskites consisting of octahedral monolayers have been realized on 3D perovskites. By bar-coating a Dion–Jacobson (DJ) phase 2D perovskite precursor solution onto 3D perovskite thin films, the conversion of the top layer of 3D perovskite to 2D perovskite was promoted, and the optimal 2D/3D heterostructure could be fabricated. The orientation of the DJ 2D perovskite could be controlled horizontally or obliquely according to the 3D perovskite template thin films; the 2D perovskite was obliquely oriented on (200)/(112)-oriented CH3NH3PbI3, and horizontally oriented on (110)-oriented CH3NH3PbI2.5Cl0.5. This approach would boost the stability and power conversion efficiency of 2D/3D heterostructures.

Additive Engineering for High‐Performance Two‐Dimensional Dion–Jacobson Pb–Sn Alloyed Perovskite Solar Cells

Two‐dimensional perovskite materials attract great attentions for the application of perovskite solar cells (PSCs) due to the regulable bandgap and high stability. However, the power conversion efficiency (PCE) of 2D PSCs is far behind in that of three‐dimensional PSCs. Herein, Dion–Jacobson (DJ) phase Pb–Sn perovskite of (PhDMA)MA4(Pb0.5Sn0.5)5I16 in 2D PSCs is introduced, which has suitable bandgap of 1.27 eV and offers the candidate for the absorber of bottom device in all perovskite tandem solar cells. The nonlinear bandgap behavior of 2D Pb–Sn perovskite materials is certified by adjusting the recipe of precursors to vary the bandgap of perovskite films. Moreover, MACl is employed to improve the film quality of 2D Pb–Sn perovskite, leading to the suppression of the defect density and nonradiative recombination for 2D PSCs. As a result, a high PCE of 12.2% is achieved for DJ phase 2D Pb–Sn PSCs.

Cesium-doped Dion-Jacobson 2D perovskites for highly stable photovoltaics with an 18.3% efficiency

Dion-Jacobson (DJ) phase 2D layered perovskites have recently emerged as promising candidates for tackling unstable issue of perovskite solar cells (PSCs) owing to their outstanding stability compared to widely studied Ruddlesden-Popper (RP) 2D and 3D analogues. To further improve the efficiency and stability of DJ 2D PSCs, we herein report a series of cesium-doped DJ 2D perovskites (PDA)Csx(MA)3−xPb4I13 (PDA=1,3-propanediammonium) and investigate Cs doping effects on material properties and device performances. The 5% Cs-doped DJ 2D PSC delivers a maximum efficiency of 18.30%, higher than the counterpart without Cs doping. Moreover, unencapsulated devices are remarkably stable, retaining ∼95% of initial efficiencies under continuous one-sun illumination for 5000 h, damp heat at 85 °C & 85% relative humidity for 240 h, and MPP tracking for 1000 h. The excellent efficiency and stability are ascribed to improved film morphology and crystallographic orientation, longer charge carrier lifetime, and reduced nonradiative recombination, induced by the Cs doping. This work demonstrates that doping Cs into DJ 2D perovskites is a facile and effective strategy towards efficient and extremely stable 2D PSCs.

2D Dion–Jacobson CsPbI3 with Enhanced Interlayer Coupling for Stable and Efficient Photovoltaics

AbstractInorganic 2D layered CsPbI3 is awaiting to overcome the phase instability of traditional 3D components. However, the most reported Ruddlesden–Popper (RP) phase 2D CsPbI3 leads to larger interlayer distance and weaker interlayer coupling since the existence of the van der Waals gap, which deteriorates the performance of the device and makes the improvement of stability unsatisfactory. Herein, this work resorts ethylenediamine cations (EDA2+) to construct a series of Dion–Jacobson (DJ) phase 2D CsPbI3 as (EDA)Csn−1PbnI3n+1 with van der Waals gap eliminated. Combining simulation calculations and experiments, it is found that the (EDA)Csn−1PbnI3n+1 has enhanced intermolecular forces to overcome the problem of insufficient crystallization power caused by large steric hindrance in the film assembly process compared to phenethylammonium‐based RP phase analogues. In addition, profit from the reduced interlayer distance and stronger coupling, the rigidity of the structure is increased, and the annoying non‐radiative recombination caused by structural fluctuations is alleviated. As a result, the 2D layered DJ phase CsPbI3‐based solar cells deliver eminent performance than RP phase analogues, especially the 2D (EDA)(Cs)4Pb5I16 (n = 5) device exhibits a record PCE of 10.43% in this work, and significantly enhanced stability.

DFT study of the structural, electronic and optoelectronic properties of PDAPb(I1−x Br x )4 perovskites

PDAPb(I1−x Br x )4 (NH3CH2CH2CH2NH3Pb(I1−x Br x )4, 0 ⩽ x ⩽ 1) is a two-dimensional Dion–Jacobson phase perovskite that has attracted extensive attention owing to its potential as a promising candidate for optoelectronic (OE) application. Herein, the structural, electronic, and optoelectronic properties of PDAPb(I1−x Br x )4 by gradually substituting I with Br at 1/4 intervals starting from PDAPbI4 based on the first-principles approach of density functional theory. With the increase in Br content, the crystal volume of PDAPb(I1−x Br x )4 decreases nonlinearly. The electronic structure shows the bandgap presents an increasing trend (PDAPbI4 (2.272 eV)–PDAPb(I0.5Br0.5)4 (2.475 eV)–PDAPbBr4 (2.678 eV)). The most stable structure that can be obtained from the calculated formation energy (E f) is PDAPb(I0.5Br0.5)4. The partial density of states reveals that the contribution of electrons is mainly related to the [PbX6]4− (X = I, Br) octahedron. The organic molecule PDA is almost not involved in the conductivity. The optoelectronic properties indicates that the characteristic peaks of the optoelectronic parameters of PDAPb(I1−x Br x )4 coincide with the bandgap. The doping ratio of 0.5 not only has the largest dielectric coefficient, but also has good conductivity in the visible region. Therefore, PDAPb(I0.5Br0.5)4 is extremely promising for applications in OE industry. This study provides some theoretical guidance for experiments and the search for new efficient and environmentally friendly OE materials.

Dion-Jacobson phase lead-free halide (PDA)MX4 (M=Sn/Ge; X=I/Br/Cl) perovskites: A first-principles theory

Hybrid lead (Pb) halide perovskites are widely regarded as promising materials for next generation of photovoltaic (PV) and optoelectronic (OE) devices owing to their high power conversion efficiency (PCE). To obtain green lead-free and excellent materials, the structural, electronic and optical properties of tin (Sn) and germanium (Ge) based single-layer Dion-Jacobson (DJ) phase perovskites (PDA)MX4 (M ​= ​Sn/Ge; X ​= ​I/Br/Cl) systems are investigated by carrying out first-principles theory. The calculation results indicate that all perovskites (PDA)MX4 have good thermal stability (at 300K), and the structural stability increases in the order of I–Br–Cl. These compounds are direct bandgap semiconductors, ranging from 1.26 to 1.81 ​eV ((PDA)SnX4) and 1.44–2.26 ​eV ((PDA)GeX4). Density of states (DOS) reveals that the band edge state mainly comes from the M-X bond and the organic molecule PDA is not directly involved in the contribution. Compared to Ge-based perovskites, the bandgap range of Sn-based perovskites is not only closer to the optimal bandgap requirement for perovskite solar cells (PSCs), but the optical properties reveal a slightly higher absorption coefficient for Sn-based perovskites in the visible light range. This suggests that (PDA)SnX4 perovskites are more favorable for PSCs applications. The theoretical study can provide strong support for the development of high-level perovskites materials in PV and OE devices.

Progress and challenges in layered two-dimensional hybrid perovskites

Dimensionality is the game-changer property of a material. The optical and electronic properties of a compound get dramatically influenced by confining dimensions from 3D to 2D. The bulk 3D perovskite materials have shown remarkable up-gradation in the power conversion efficiency, hence grabbing worldwide attention. But instability against moisture, temperature, and ion migration are the factors constantly back-stabbing and hindering from full-scale commercialization. 2D perovskite material has emerged as an excellent bridging entity between structural-chemical stability, and viable commercialization. Organic–inorganic 2D perovskite materials come with a layered structure in which a large organic cation layer as a spacer is sandwiched between two inorganic metal halide octahedra layers. Moreover, hydrophobic spacer cations are employed which isolate inorganic octahedral layers from water molecules. Hydrophobic spacer cations protect the authentic structure from being degraded. These layered structures occur in two phases namely the Ruddlesden–Popper phase and Dion–Jacobson phase, depending on the spacer cation types. Alternating inorganic and organic layers form multiple quantum wells naturally, along with spin–orbit-coupling gives Rashba splitting. 2D perovskite materials are coming up with interesting chemical, physical properties like exciton dynamics, charge carrier transport, and electron–phonon coupling as a result of the quantum confinement effect. Despite appreciable stability, limited charge transport and large bandgap are limiting the application of 2D perovskite materials in solar cells. These limitations can be overcome by using the concept of 2D/3D multidimensional hybrid perovskites, which includes the long-term stability of 2D perovskite and the high performance of 3D perovskite at the same time. Here in this perspective, we have given brief insight on structural versatility, synthesis techniques, some of the unique photophysical properties, potential device fabrication, and recent advancements in the 2D structure to stand against degradation. Certain shortcomings and future outlooks are also discussed to make the perspective more informative.

Structural, electronic and optoelectronic properties of asymmetric organic ligands in Dion-Jacobson phase perovskites

Dion-Jacobson (DJ) phase perovskites have attracted substantial attention in view of its showing great potential to solve the stability issue of optoelectronic devices. Herein, three organic ligands (1,3-propanediamine PDA, N-methylpropane-1,3-diammonium N-MPDA, and 3-(dimethylamino)-1-propylammonium DMPD) are selected as a spacer cation. The structural, electronic, and optoelectronic properties of organic ligands with different degrees of symmetry in n = 1 Dion-Jacobson (DJ) phase A'PbI4 (A' = PDA, N-MPDA, DMPD) perovskite are investigated by carrying out the first-principles method. The structural parameters show an increasing trend of crystal volume, octahedral distortion and stability of the crystal structure with the increase of ligand asymmetry. All three kinds of perovskites are direct bandgap semiconductors, and the bandgap values of A'PbI4 are in the order of N-MPDAPbI4 (2.711 eV) > PDAPbI4 (2.272 eV) > DMPDPbI4 (2.201 eV). The density of states (DOS) indicates that the 6p and 6s orbitals of Pb atoms and 5p orbitals of I atoms are mainly involved in conduction, while the contribution of organic ligands to electron orbitals is negligible. Additionally, the optoelectronic properties reveal that perovskite with asymmetric organic ligands has better absorption in the visible region than perovskite with symmetric organic ligands, which makes it useful as photovoltaic materials. The calculation of asymmetric organic ligands provides guidance and insights for the study of high-performance DJ phase perovskite.

2D Graphene-Like Pb-Free Perovskite Semiconductor CsSb(Br1-xIx)4 with Quasi-linear Electronic Dispersion and Direct Bandgap Close to Germanium.

Thanks to its ultrahigh carrier mobility (∼104-105 cm2 V-1 s-1), graphene shows tremendous application potential in nanoelectronics, but it cannot be applied in effective field-effect transistors (FETs) because of its intrinsic gapless band structure. Thus, introducing a bandgap for graphene is a prerequisite to realize an FET for logic applications. Herein, through first-principles GW calculations, we have predicted a series of novel Dion-Jacobson (DJ) phase halide perovskite semiconductors CsSb(Br1-xIx)4 (x = 0, 0.5, 1) with the quasi-linear (graphene-like) band edge dispersion; as the best one of which, CsSbBr2I2 exhibits a direct bandgap (0.52 eV) as well as a quasi-linear electronic dispersion, yielding an ultrasmall carrier effective mass (0.03 m0) and a high estimated carrier mobility (5 × 103 cm2 V-1 s-1). This gives a significant reference to the exploration of semiconductors with excellent transport properties. Moreover, our calculations also implicate that the DJ perovskites CsSb(Br1-xIx)4 (x = 0, 0.25, 0.5, 0.75, 1) show soft and anisotropic mechanical characteristics as well as excellent electronic, transport, and optical properties, which demonstrate their multifunctional application in infrared optoelectronic, high-speed electronics, and photovoltaics.

Formamidinium Perovskitizers and Aromatic Spacers Synergistically Building Bilayer Dion-Jacobson Perovskite Photoelectric Bulk Crystals.

Two-dimensional (2D) multilayer Dion-Jacobson (DJ) phase organic inorganic hybrid perovskites (OIHPs) have attracted extensive research attention due to the high stability and excellent charge-transport properties in the optoelectronic field. However, the synthesis of 2D multilayer DJ OIHPs is still very challenging. Until now, only few multilayer DJ perovskites have been reported and most of them are based on volatile methylamine (MA) cations. Compared with MA-based OIHPs, the OIHPs constructed with formamidinium (FA) as perovskitizers not only improve the stability but also extend the light absorption range. Meanwhile, the introducing aromatic diamines as spacers could promote the electron-hole separation in such DJ hybrids. However, the DJ OIHP bulk single crystal constructed by using the advantages of FA as perovskitizers and aromatic diamines as spacers is still blank. Herein, we integrate the properties of organic cations and inorganic skeletons at a molecular-scale to construct a broadband-responsive 2D bilayer DJ perovskite (3AMPY)(FA)Pb2I7 [3AMPY = 3-(aminomethyl)pyridinium], which shows a fascinating detectivity from X-ray (5.23 × 104 μC Gyair-1 cm-2 at 200 V bias) and visible light (6 × 1012 jones at 637 nm) to the near-infrared region (2.6 × 109 jones at 780 nm). After an in-depth analysis of structure and optical properties, we found that the distortion degree of Pb-I-Pb bond angles between adjacent PbI6 octahedra plays a crucial role on optical properties; on the other hand, the interlayer spacer cations (3AMPY) and intralayer perovskitizers (FA) mutual participate in the contribution of the conduction band, making (3AMPY)(FA)Pb2I7 have a narrow optical band gap of 1.54 eV. Such a 2D perovskite material with a wide spectra response will be the preferred choice for photodetection under complex conditions.

High Efficiency Perovskite Solar Cells Employing Quasi‐2D Ruddlesden‐Popper/Dion‐Jacobson Heterojunctions

AbstractWhile 2D Ruddlesden‐Popper (RP) perovskites exhibit attractive opto‐electronic properties and stability for use in perovskite solar cells (PSCs), their complicated film‐forming processes often induce a non‐negligible level of defects that significantly undermine the power conversion efficiency (PCE) and stability of PSCs. Here, the use of two organic ammonium salts with the same chain length, namely monoammonium (butylammonium iodide, BAI) and diammonium (1,4‐butanediamine dihydroiodide, BDAI2) for surface defect passivation of RP‐2D perovskite films of (AA)2MA4Pb5I16 (n = 5) are reported. It is found that the diammonium BDAI2 not only effectively reduces the defect density (similarly to using monoammonium BAI) but forms a Dion‐Jacobson (DJ) 2D structure to enhance interfacial charge extraction and suppress surface charge recombination. As a result, a boosted PCE of 18.34% has been obtained with a high open‐circuit voltage of 1.24 V. Owing to the enhanced structural integrity of the DJ phase, the RP‐2D/DJ‐2D perovskite heterojunction films exhibit supreme material robustness, which translates to the impressive environmental stability of devices, showing nearly zero‐degradation of the efficiency after 800 h of continuous thermal aging (60 °C) for 800 h. This work enriches the fundamental understanding of the impacts of the DJ‐2D structure on the surface properties of 2D perovskites.