Single Perovskite Layers Research Articles

Optimized preparation of La3Mn2O7 with superior lattice oxygen mobility and adsorbed oxygen utilization for catalytic removal of toluene

The R-P type layered perovskite La3Mn2O7 (LLM) is considered a more promising toluene oxidation catalyst than perovskite LaMnO3 (LMO) due to the versatile environment it provides for oxygen atoms, yet the challenge of realizing an optimal synthesis route remains. Herein, we revealed how calcination temperature influenced the structure–activity relationship and the mechanism by which the layered structure enhanced oxygen species reactivity. LLM700 possesses optimal toluene adsorption performance, oxygen species activation capability and low-temperature reducibility, thus exhibiting the highest catalytic activity (T90 = 283 °C) among single layered perovskite catalysts. The large interlayer gaps in the layered structure, combined with the weaker Mn-O bond strength near the layered structure, facilitate the easy removal of oxygen atoms, creating oxygen vacancies that act as pathways for oxygen ions to migrate within the lattice. Together, these factors enable the layered structure to enhance the mobility of lattice oxygen and the utilization of adsorbed oxygen, making LLM an ideal model for catalyzing the oxidation of toluene. Furthermore, the possible reaction pathway for the oxidation of toluene on LLM700 was inferred using GC–MS. This work paves the way for the catalytic applications of layered perovskites.

Design and optimization of all-inorganic lead-free perovskite solar cells with RbGeI3/KSnI3 heterojunction structure

Currently, the performance of inorganic and non-toxic perovskite solar cells (PSCs) lags far behind that of organic and Pb-containing PSCs. To enhance the photovoltaic capabilities of inorganic and non-toxic perovskites, a fully inorganic RbGeI3/KSnI3 heterojunction without hole transport layer is proposed, and simulation and optimization are performed using SCAPS-1D software. Research findings indicate that the RbGeI3/KSnI3 perovskite heterojunction significantly improves the quantum efficiency compared to single-layer perovskite, and due to the more matched energy levels, it improves the electric field of the cell and is more conducive to the migration of photogenerated carriers, resulting in excellent device performance. Moreover, PSCs undergo optimization across multiple parameters, including materials for the charge transport layer, perovskite layer thickness, defect density, bandgap, operating temperature, and so on. This comprehensive approach involves analyzing changes in electric field, band structure, and recombination rate. Finally, the power conversion efficiency of the optimized device achieves 40.44 %, marking a significant 440 % increase compared to the 7.49 % efficiency of single-layer PSCs. This work proposes a heterojunction structure to create efficient inorganic and non-toxic perovskite solar cells, providing a novel strategy for further development in this field.

2D organic-inorganic lead perovskite: Advancing X-ray detection capability

Two-dimensional (2D) perovskite single crystals have risen to be prominent in the domain of optoelectronic materials due to their exceptional characteristics including notably low ion migration and defect density. A distinguishing feature is the strategic inclusion of larger organic amine spacer, alternately inserted between inorganic lead halide octahedral layers. This spacer effectively mitigates ion migration, even under higher bias voltages, which is particularly advantageous for X-ray detection. However, the simultaneous realization of multiple functions within this realm remains a formidable challenge. In this work, we have synthesized a high-quality organic spacer-incorporated single layered 2D perovskite single crystal of [CYP]PbBr4 (CYP = 1-cyclohexylpiperazine). Our findings reveal the impressive potential of [CYP]PbBr4 in the domain of X-ray detection, as evidenced by the ultrahigh X-ray sensitivity, long-term stability, and astonishingly low detection limit of 1.72 nGyairs-1. Notably, [CYP]PbBr4 also emits bright broadband yellow light with quantum yield of 30.3%, and the fabricated white LED achieves a high Color Rendering Index of 94.1, which surpasses that of commercially available white LED based on YAG: Ce3+ (< 80).

Thickness dependent numerical investigations of lead free perovskite/CIGS bilayer solar cell using SCAPS-1D

Due to the toxicity and the complex fabrication process lead-based perovskite solar cells are difficult to fabricate commercially though the power conversion efficiency has reached 25.2 ​%. In the current scenario, lead free perovskite solar cell devices are gaining interest among the researchers and the bilayer structure is showing significant improvement in the efficiency. In this work, with the help of SCAPS 1D, a lead free single-layer perovskite (CH3NH3SnBr3) solar cell and a bilayer structure (CH3NH3SnBr3/CIGS) have been investigated to compare the photovoltaic performance by using PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) and SnTe as an electron transport layer (ETL) and hole transport layer (HTL) respectively. Different device parameters i.e. thickness, defect density, doping concentration and series-shunt resistance of the device was optimized to obtain the best performance. In the case of a single absorber layer, power conversion efficiency (PCE), open circuit voltage (Voc), fill factor (FF) and the short circuit current density (Jsc) were achieved 20.58 ​%, 0.931 ​V, 64.95 ​% and 34.03 mA.cm−2 respectively. However, it is observed that bilayer structure (FTO/PCBM/CH3NH3SnBr3/CIGS/ZnTe/SnTe/Au) obtains 22.68 ​% of PCE, 0.916 ​V of Voc, 71.46 ​% of FF and 34.66 mA.cm−2 of Jsc. This study suggests that a proper bilayer structure is beneficial to improve the device performance in terms of Jsc and FF by increasing the carrier generation and reducing the back surface field recombination.

A novel perovskite solar cell comprising CsPbI2Br/Cs2SnI6 (CsGeI3) cascade absorbing bilayer and Cr2O3 electron transport material: A theoretical comparison study

In order to prevent the limitation on absorbing energies by a single-layer perovskite solar cells (PSCs), a cell comprising bilayer heterostructure in the form of FTO/Cr2O3/CsPbI2Br +Cs2SnI6 (CsGeI3)/spiro-OMeTAD/Au is simulated and its photovoltaic performance including incident photon-to-current conversion efficiency, fill factor, open circuit voltage and short circuit current is evaluated using SCAPS 1D software package. It is shown by introducing these structures, not only a wider range of the sunlight spectrum is exploited, but also by achieving a favorable band-edge bending as graded band gap, more charge carriers can be collected. Moreover, further improvement in the performance of devices is obtained by optimizing the thickness of absorbing layers and work function of the back electrode. The thermal stability of PSCs is investigated by varying the temperature in the range of 300–480 K and the effect of various electron transport materials (ETMs) on the performance of the cell is evaluated. Under optimized condition, it is found that the efficiencies of the cells with CsPbI2Br+Cs2SnI6 and CsPbI2Br+CsGeI3 bilayer heterostructures increase from 13.38% for non-heterojunction structure to 15.14% and 16.34%, respectively. Furthermore, the simulation results reveal that the photovoltaic cell made of CsPbI2Br+CsGeI3 absorbing layer having higher efficiency and greater thermal stability (compared to PSC made of CsPbI2Br+Cs2SnI6 absorbing layer) is an appropriate and promising candidate as efficient perovskite solar cell.

Co-doping effect of Ce ions on Eu ion-doped Sr2SnO4 in terms of emission color tunability and intensity modulation

We investigated the co-doping effect of Ce3+ and Eu3+ ions on the visible emission of the single-layered perovskite Sr2SnO4. The Ce3+ single-doped Sr2SnO4 showed a sizable feature at approximately 260 nm in the photoluminescence excitation spectra and a broad peak at approximately 400 nm in the photoluminescence spectra. These peaks were attributed to the 4f–5d transitions of Ce3+. In the Ce3+ and Eu3+ co-doped samples, as the concentration of Ce3+ increased, the emission intensity of Eu3+ increased drastically with near-ultraviolet excitation due to the energy transfer from Ce3+ to Eu3+. Because of the changes in the relative emission intensities of the two ions, the colors emitted by phosphor were tuned from blue/orange to red. We also discussed the effect of Ce3+ doping on the photochromic behavior of Eu3+-doped Sr2SnO4, together with luminescence modulation.

Improved Photocatalytic O2 Evolution on a Sillén–Aurivillius Perovskite Oxychloride Bi6NbWO14Cl by Rh2O3 Additives and Surface Modifications

A Sillén–Aurivillius-type single-layered perovskite oxyhalide, Bi6NbWO14Cl, was recently reported as a stable and efficient O2-evolving photocatalyst for Z-scheme water splitting, even without any modifications. However, efforts have not yet been made to improve its photocatalytic activity. In this study, we synthesized a Bi6NbWO14Cl photocatalyst using Rh2O3 additives and modified its surface with Rh species to improve its photocatalytic activity. An appropriate amount of the Rh2O3 additive significantly enhanced the O2 evolution rate on Bi6NbWO14Cl from the aqueous AgNO3 solution, likely owing to enhanced charge transfer by the metallic Rh nanoparticles formed around the grain boundaries. In addition, surface modification with Rh species led to a further enhancement of the O2 evolution rate. The apparent quantum efficiency of the O2 evolution reached 11% at 420 nm, which is the best reported performance for oxyhalides prepared by solid-state reactions. These Rh species were characterized by X-ray absorption fine structure, X-ray photoelectron spectroscopy, and transmission electron microscopy, and their roles in the enhanced photocatalytic activities were discussed.

Development of titanium-doped SmBaMn2O5+δ layered perovskite as a robust electrode for symmetrical solid oxide fuel cells

It is a big challenge ahead of finding a symmetric electrode material that optimally works as both anode and cathode, with excellent structural and chemical stability and high catalytic activity. Herein, we propose a high-performance symmetric electrode material, SmBaMn1.9Ti0.1O5+δ (SBMTi), with a single A-site layered perovskite phase in both reducing and oxidizing atmospheres. Owing to the high binding energy, titanium doping can enhance the structural stability and improve the catalytic activity to the hydrogen oxidation and oxygen reduction processes. The simple Ti-doping strategy enables a dramatic reduction in stoichiometric oxygen change upon oxidizing and reducing atmosphere alternation, and a considerable decrease in thermal expansion coefficient. The symmetrical cell with SBMTi electrode can provide a maximum power density of 603 mW cm−2 at 900 °C, and shows a relatively stable thermal-cycle and atmosphere alternation performance. The developed SmBaMn1.9Ti0.1O5+δ shows great potential as symmetric electrode in symmetrical solid oxide fuel cells.

Hybrid perovskites as oxygen evolution electrocatalysts for high-performance anion exchange membrane water electrolyzers

Highly active and platinum group metal-free (PGM-free) oxygen evolution reaction (OER) electrocatalysts are essential for producing low-cost and clean hydrogen in anion exchange membrane water electrolyzers (AEMWEs). Thanks to the unique characteristics of perovskite oxides, which include low cost, tunable electronic structure and cation deficiency, high electronic conductivity, high durability, high specific catalytic activity, and environmental friendliness, they have been widely designed and employed as the OER electrocatalysts. Here, a set of novel hybrid perovskites, LaxSr4-xNiyFe3-yO10-δ (LxS4-xNyF3-y), were demonstrated, which consist of a single-layer perovskite phase (P phase) and two Ruddlesden–Popper perovskite phases (RP phases). These hybrid perovskites synergize the advantages of the P phase and RP phases, which improves the oxygen-ion diffusion rate, leading to enhanced OER activity. Furthermore, the concentration of each phase can be tuned by alternating the compositional stoichiometry. A relatively uniform distribution of the P phase and RP phases can maximize the interfacial area and achieve the highest oxygen-ion diffusion rate. L3S1N2F1, L2S2N1F2, and L2S2N1.5F1.5 exhibit outstanding OER activity, which achieve 10 mA/cm2 at a low overpotential of less than 360 mV in 1.0 M KOH. Additionally, herein, the hybrid perovskites are implemented as the anodes of AEMWEs, which deliver an exceptional current density of > 1.0 A/cm2 at 1.8 V.

Impact of photon recycling on the light extraction from metal halide perovskite light emitting diodes

The impact of photon recycling on the efficiency of light extraction from metal halide perovskite light emitting diodes is quantified using a novel modelling framework based on a detailed-balance compatible Green dyad approach. Analysis of photon modes contributing to internal emission and iterative evaluation of re-absorption and re-emission processes is performed for single perovskite layers in absence and presence of a metallic reflector and under consideration of associated parasitic absorption losses. Finally, the approach is employed to characterize the emission characteristics of a realistic multilayer device stack in dependence of the emitter thickness.

Graded multilayer triple cation perovskites for high speed and detectivity self-powered photodetector via scalable spray coating process

Rapid advancements in perovskite materials have led to potential applications in various optoelectronic devices, such as solar cells, light-emitting diodes, and photodetectors. Due to good photoelectric properties, perovskite enables low-cost and comparable performance in terms of responsivity, detectivity, and speed to those of the silicon counterpart. In this work, we utilized triple cation perovskite, well known for its high performance, stability, and wide absorption range, which is crucial for broadband photodetector applications. To achieve improved detectivity and faster response time, graded multilayer perovskite absorbers were our focus. Sequential spray deposition, which allows stacked perovskite architecture without disturbing lower perovskite layers, was used to generate single, double, and triple-layer perovskite photodetectors with proper energy band alignment. In this work, we achieved a record on self-powered perovskite photodetector fabricated from a scalable spray process in terms of EQE and responsivity of 65.30% and 0.30 A W-1. The multilayer devices showed faster response speed than those of single-layer perovskite photodetectors with the champion device reaching 70 µs and 88 µs for rising and falling times. The graded band structure and the internal electric field generated from perovskite heterojunction also increase specific detectivity about one magnitude higher in comparison to the single-layer with the champion device achieving 6.82 × 1012 cmHz1/2 W−1.

Tunable phase transition temperature and nonlinear optical properties of organic–inorganic hybrid perovskites enabled by dimensional engineering

Improving the phase transition temperature and enriching optoelectronics properties have become the top priorities. Herein, we have successfully synthesized two bilayer (2D/3D) perovskite materials based on a single layer perovskite.

Lead-free Double Perovskite Cs2 AgIn0.9 Bi0.1 Cl6 Quantum Dots for White Light-Emitting Diodes.

Perovskite‐based optoelectronic devices have attracted considerable attention owing to their excellent device performances and facile solution processing. However, the toxicity and intrinsic instability of lead‐based perovskites have limited their commercial development. Moreover, the provision of an efficient white emission from a single perovskite layer is challenging. Here, novel electrically excited white light‐emitting diodes (WLEDs) based on lead‐free double perovskite Cs2AgIn0.9Bi0.1Cl6 quantum dots (QDs) without any phosphor are fabricated for the first time. Density functional theory calculations are carried out to clarify the mechanism of absorption and recombination in Cs2AgIn0.9Bi0.1Cl6 with Bi‐doping breaking the parity‐forbidden transition of the direct bandgap. Microzone optical and electronic characterizations reveal that the broadband emission of Cs2AgIn0.9Bi0.1Cl6 QDs originates from self‐trapped excitons, and luminescent properties are unchanged after the film deposition. The QD‐WLED exhibits excellent Commission Internationale de L'Eclairage color coordinates, correlated color temperature and relatively high color rendering index of (0.32, 0.32), 6432 K, and 94.5, respectively. The maximum luminance of 158 cd m−2 is achieved by triphenylphosphine oxide passivation, and this lead‐free QD‐WLED exhibits a superior stability in ambient air with a long T 50 ≈48.53 min. Therefore, lead‐free perovskite Cs2AgIn0.9Bi0.1Cl6 QDs are promising candidates for use in WLEDs in the future.

Realizing White Emission of Single-Layer Dual-Color Perovskite Light-Emitting Devices by Modulating the Electroluminescence Emission Spectra.

Dual-color emission in a single perovskite layer would make perovskite light-emitting devices (PLEDs) more competitive compared with other display technologies. However, due to the carrier dynamics in a blended perovskite film and the low reaction activation energy of the halide exchange reaction, it is very difficult to achieve the dual-color emission in a perovskite layer. Here, dual-color electroluminescence (EL) emission in a single perovskite layer has been realized by slowing the energy transfer from wide-bandgap energy levels to narrow-bandgap energy levels. Moreover, the EL spectra can be controlled by modulating the composition of the perovskite layer. When the amount of CH3NH3I(MAI) in the precursor was varied, white emission with CIE coordinates of (0.33, 0.34) could be achieved. Our work proposes a new strategy for white emission from PLEDs. Also, the analysis and discussion of carrier dynamics in this work may help to enhance our understanding of the working mechanism of PLEDs.

Pure Blue Electroluminescence: Pure Blue Electroluminescence by Differentiated Ion Motion in a Single Layer Perovskite Device (Adv. Funct. Mater. 31/2021)

In article number 2102006, Jason D. Slinker and co-workers leverage CsPbBr3−xClx perovskites, polyelectrolytes, and a salt additive to demonstrate pure blue emission from single-layer light-emitting electrochemical cells. The electrolytes transport the ions from salt additives, enhancing charge injection and stabilizing the inherent perovskite emissive lattice for highly pure and sustained blue emission. The resulting pure blue emission meets the US NTSC blue standard benchmark.

B-Site Cation Ordering in Films, Superlattices, and Layer-by-Layer-Grown Double Perovskites

The preparation of cation-ordered thin films of correlated oxides is of great interest for both fundamental and applied research. The scientific long-term vision is strongly motivated by the perspective of studying electronic correlations in condensed matter without the presence of chemical or quenched disorder. A promising material platform provides double perovskite A2BB’O6 bulk samples with different types of B/B’ ordering. However, the growth of A- and/or B-site-ordered correlated oxide thin films is known to be a challenging task. In this review, we evaluate the growth of double perovskite A2BB’O6 thin films by means of well-elaborated physical vacuum deposition techniques, such as pulsed laser deposition (PLD) and sputtering and compare them with a close-to-equilibrium growth with the metalorganic aerosol deposition (MAD) technique. The latter was further developed to grow an emergent interfacial double perovskite phase in LaNiO3/LaMnO3 superlattices, and finally, by way of a layer-by-layer route. The growth of La2CoMnO6 films on SrTiO3(111) substrates by sequential deposition of single perovskite layers of LaCoO3/LaMnO3/LaCoO3/… was demonstrated and the film properties were compared to those obtained within the state-of-the art growth mode.

Pure Blue Electroluminescence by Differentiated Ion Motion in a Single Layer Perovskite Device

AbstractBlue electroluminescence is highly desired for emerging light‐emitting devices for display applications and optoelectronics in general. However, saturated, efficient, and stable blue emission has been challenging to achieve, particularly in mixed‐halide perovskites, where intrinsic ion motion and halide segregation compromises spectral purity. Here, CsPbBr3−xClx perovskites, polyelectrolytes, and a salt additive are leveraged to demonstrate pure blue emission from single‐layer light‐emitting electrochemical cells (LECs). The electrolytes transport the ions from salt additives, enhancing charge injection and stabilizing the inherent perovskite emissive lattice for highly pure and sustained blue emission. Substituting Cl into CsPbBr3 tunes the perovskite luminescence from green through blue. Sky blue and saturated blue devices produce International Commission on Illumination coordinates of (0.105, 0.129) and (0.136, 0.068), respectively, with the latter meeting the US National Television Committee standard for the blue primary. Likewise, maximum luminances of 2900 and 1000 cd m−2, external quantum efficiencies (EQEs) of 4.3% and 3.9%, and luminance half‐lives of 5.7 and 4.9 h are obtained for sky blue and saturated blue devices, respectively. Polymer and LiPF6 inclusion increases photoluminescence efficiency, suppresses halide segregation, induces thin‐film smoothness and uniformity, and reduces crystallite size. Overall, these devices show superior performance among blue perovskite light‐emitting diodes (PeLEDs) and general LECs.

2D Lead Iodide Perovskite with Mercaptan-Containing Amine and Its Exceptional Water Stability.

Two dimensional (2D) hybrid perovskites have attracted a great deal of interest because of their appropriate photovoltaic efficiency and environmental stability. Although some 2D hybrid perovskites with sulfur-containing amines have been reported, the cation having the mercaptan group has not been well explored yet. In this work, cysteamine (Cya, HS(CH2)2NH2), a mercaptan-containing amine, was introduced into 2D hybrid perovskite. Two 2D lead iodides with different structures, (HCya)2PbI4 (1) and (HCya)7Pb4I15 (2), were isolated as a red low-temperature phase and a yellow high-temperature phase, respectively. X-ray single-crystal structural analysis showed that the red phase 1 is a single layered corner-shared perovskite and that the yellow phase 2 is a corner/edge-shared quasi-2D perovskite. A thermo-induced reversible 1 to 2 phase transition was found in this synthetic system. The configuration of HCya cation greatly influences the crystallization equilibrium, generating different structures of the lead halides. The single-crystal structure of 1 is discussed in comparison with that of (HAE)2PbI4 (AE = HO(CH2)2NH2), an analogue of 1. The different effects of OH and SH groups on the 2D frameworks are studied based on their hydrogen bonding properties. More remarkably, although the two perovskites have similar structures, the (HCya)2PbI4 (1) has an intrinsic water stability that is much more stable than (HAE)2PbI4, which should be attributed to the affinity of the SH group with lead on the surface of the lead halide.

Layer number dependent ferroelasticity in 2D Ruddlesden\u2013Popper organic-inorganic hybrid perovskites

Ferroelasticity represents material domains possessing spontaneous strain that can be switched by external stress. Three-dimensional perovskites like methylammonium lead iodide are determined to be ferroelastic. Layered perovskites have been applied in optoelectronic devices with outstanding performance. However, the understanding of lattice strain and ferroelasticity in layered perovskites is still lacking. Here, using the in-situ observation of switching domains in layered perovskite single crystals under external strain, we discover the evidence of ferroelasticity in layered perovskites with layer number more than one, while the perovskites with single octahedra layer do not show ferroelasticity. Density functional theory calculation shows that ferroelasticity in layered perovskites originates from the distortion of inorganic octahedra resulting from the rotation of aspherical methylammonium cations. The absence of methylammonium cations in single layer perovskite accounts for the lack of ferroelasticity. These ferroelastic domains do not induce non-radiative recombination or reduce the photoluminescence quantum yield.

Solution-Processed Perovskite/Perovskite Heterostructure Via a Grafting-Assisted Transfer Technique

The outstanding properties of perovskites have attracted huge attention in optoelectronic applications. However, the current study mainly focuses on small-area single-layer perovskite films. Surfac...