Perovskite Nanomaterials Research Articles

Synthesis and Characterization of High-Efficiency Halide Perovskite Nanomaterials for Light-Absorbing Applications.

Inorganic perovskite materials are possible candidates for conversion of solar energy to electrical energy due to their high absorption coefficient. Perovskite solar cells (PSCs) introduced a new type of device structure that has attention due to better efficiencies and interest in PSCs that has been increasing in recent years. Halide perovskite materials such as CsPbIBr2 show remarkable optical and structural performance with their better physical properties. Perovskite solar cells are a possible candidate to replace conventional silicon solar panels. In the present study, CsPbIBr2 perovskite materials' thin films were prepared for light-absorbing application. Five thin films were deposited on the glass substrates by subsequent spin-coating of CsI and PbBr2 solutions, subsequently annealed at different temperature values (as-deposited, 100, 150, 200 and 250 °C) to get CsPbIBr2 thin films with a better crystal structure. Structural characterizations were made by using X-ray diffraction. CsPbIBr2 thin films were found to be polycrystalline in nature. With increasing annealing temperature, the crystallinity was improved, and the crystalline size was increased. Optical properties were studied by using transmission data, and by increasing annealing temperature, a small variation in optical band gap energy was observed in the range of 1.70-1.83 eV. The conductivity of CsPbIBr2 thin films was determined by a hot probe technique and was found to have little fluctuating response toward p-type conductivity, which may be due to intrinsic defects or presence of CsI phase, but a stable intrinsic nature was observed. The obtained physical properties of CsPbIBr2 thin films suggest them as a suitable candidate as a light-harvesting layer. These thin films could be an especially good partner with Si or other lower band gap energy materials in tandem solar cells (TSC). CsPbIBr2 material will harvest light having energy of ∼1.7 eV or higher, while a lower energy part of the solar spectrum will be absorbed in the partner part of the TSC.

All-Inorganic Manganese-Based CsMnCl3 Nanocrystals for X-Ray Imaging.

Lead‐based halide perovskite nanomaterials with excellent optical properties have aroused great attention in the fields of solar cells, light‐emitting diodes, lasing, X‐ray imaging, etc. However, the toxicity of lead prompts researchers to develop alternatives to cut down the usage of lead. Herein, all‐inorganic manganese‐based perovskite derivatives, CsMnCl3 nanocrystals (NCs), with uniform size and morphology have been synthesized successfully via a modified hot‐injection method. These NCs have a direct bandgap of 4.08 eV and a broadband emission centered at 660 nm. Through introducing modicum lead (1%) into the CsMnCl3 NCs, the photoluminescence intensity greatly improves, and the quantum yield (PLQY) increases from 0.7% to 21%. Furthermore, the CsMnCl3:1%Pb NCs feature high‐efficiency of X‐ray absorption and radioluminescence, which make these NCs promising candidates for X‐ray imaging.

Highly Efficient and Stable Eu3+-Doped CsPbBr3/Cs4PbBr6 Perovskites for White Light-Emitting Diodes

All-inorganic halide perovskite nanomaterials have a high application potential in the field of display and lighting because of unique photoelectric properties. However, these materials suffer from problems related to poor water and thermal stabilities. In this study, green Eu3+-doped CsPbBr3/Cs4PbBr6 perovskite composites that were synthesized by a saturated recrystallization method at room temperature showed an enhanced photoluminescence quantum yield of 87% and superior water and thermal stabilities to that of undoped perovskites. Finally, green Eu3+-doped CsPbBr3/Cs4PbBr6 perovskite composites were fabricated into white light-emitting diodes (WLEDs) with a wide color gamut (124% of the National Television System Committee standard) and a high efficiency of 43.06 lm/W.

Direct optical patterning of perovskite nanocrystals with ligand cross-linkers.

Precise microscale patterning is a prerequisite to incorporate the emerging colloidal metal halide perovskite nanocrystals into advanced, integrated optoelectronic platforms for widespread technological applications. Current patterning methods suffer from some combination of limitations in patterning quality, versatility, and compatibility with the workflows of device fabrication. This work introduces the direct optical patterning of perovskite nanocrystals with ligand cross-linkers or DOPPLCER. The underlying, nonspecific cross-linking chemistry involved in DOPPLCER supports high-resolution, multicolored patterning of a broad scope of perovskite nanocrystals with their native ligands. Patterned nanocrystal films show photoluminescence (after postpatterning surface treatment), electroluminescence, and photoconductivity on par with those of conventional nonpatterned films. Prototype, pixelated light-emitting diodes show peak external quantum efficiency of 6.8% and luminance over 20,000 cd m−2. Both are among the highest for patterned perovskite nanocrystal devices. These results create new possibilities in the system-level integration of perovskite nanomaterials and advance their applications in various optoelectronic and photonic platforms.

Construction of a ternary WO3/CsPbBr3/ZIF-67 heterostructure for enhanced photocatalytic carbon dioxide reduction

Using halide perovskite nanomaterials for solar-to-fuel conversion has recently attracted a lot of attention due to their excellent photoelectric properties. However, severe photogenerated charge carrier recombinations and poor reaction kinetics greatly restrict their photocatalytic performance. In this study, a ternary WO3/CsPbBr3/ZIF-67 heterostructure was designed for efficient CO2 photoreduction. The results indicate that the Z-scheme charge transfer pathway constructed between WO3 and CsPbBr3 ensures the effective transfer and separation of photogenerated charge carriers. Meanwhile, the subsequent surface modification of zeolitic imidazolate frameworks (ZIF-67) with active Co centers further benefits CO2 adsorption and activation. Accordingly, the synergistic effects of charge separation and CO2 uptake greatly promote the photocatalytic activity. The optimal WO3/CsPbBr3/ZIF-67 heterostructure yields a CO production of 99.38 μmol g−1 in 3 h, which is 6.8 times of that produced by CsPbBr3. This work will inspire new insights in developing efficient photocatalysts for CO2 reduction and even more challenging photocatalytic reactions by elaborately regulating the functional ingredient.

Are the emission quantum yields of cesium plumbobromide perovskite nanocrystals reliable metrics for their quality?

The impact of halide perovskites on photonics, optoelectronics and energy science is indisputable. The pursuit of perovskite nanomaterials has open roads for explorations where large surface-to-volume ratios are paramount. While the solution-phase synthesis of most nanoparticles is relatively easy, the cleaning steps for obtaining populations of high-quality nanocrystals in good yields tend to present some challenges. As an extensive number of reports show, the quality of photoluminescent nanoparticles usually correlates with increased optical-emission quantum yields. Herein, we examine the products from the cleaning steps, involving centrifugation and resuspension washes, of an established procedure for preparing cesium plumbobromide nanocrystals. The photoluminescence quantum yields of the collected nanocrystals drops by about 10% to 30% after each wash. At the same time, the average exciton lifetime increases by about a factor of four, which reflects a decrease in the radiative-decay rates by about factor of five, while the non-radiative ones increase by less than a factor of two. Further analysis indicates that decreasing the particles size, along with changing their morphology, alters some of the exciton traps, or “quenching” sites, on them. This size decrease, along with changes that accompany it, shorten the exciton lifetimes while enhancing the limited spatial overlap between the holes and the electrons of the excitons and considerably increasing the radiative rates of deactivation. These findings do not suggest that good quality nanoparticles should not necessarily manifest high emission quantum yields. Rather, they point to the complexity of nanomaterials, due to their inherent heterogeneity, that warrants multimodal analysis for understanding the exciton dynamics, while correlating it to observed structural characteristics.

Optical humidity sensors based on lead-free Cu-based perovskite nanomaterials.

Organometallic halide perovskite materials possess unique and tunable optical properties with a wide range of optoelectronic applications. However, these materials suffer from humidity-driven degradation in ambient atmospheres. In this paper we investigate stable copper-based perovskite nanocrystals for potential use in humidity sensors, specifically examining their unique humidity-dependent optical properties and reversibility. We controlled stoichiometric ratios of Cu-based perovskites and demonstrated that (methylammonium)2CuBr4 nanocrystals showed excellent reversible physisorption of water molecules. These perovskite nanocrystals exhibited reversible hydro-optical properties, including transparency changes in response to variations in relative humidity under ambient conditions. The perovskite nanomaterial humidity sensor was highly reliable and stable, with a linear correlation in a relative humidity range of 7% to 98%. Accordingly, the lead-free Cu-based perovskite materials developed herein have the potential to be employed as real-time, self-consistent humidity sensors.

Evaluation of the antimicrobial potential of cerium-based perovskite (CeCuO3) synthesized by a hydrothermal method

A hydrothermally synthesized CeCuO3 perovskite nanomaterial has been used as a disinfectant against microorganisms causing urinary tract infections (UTIs).

Study of the influence of synthesis method in BaFeO3-δ perovskite on structural, optical, magnetic and antibacterial properties

In this study, the BaFeO3-δ perovskite nanomaterials sample has been synthesized by co-precipitation (Cop) and sol-gel (Sol) methods respectively. Rietveld refinements of X-ray diffraction (XRD) patterns showed that these samples crystallized in rhombohedral structure with space group R3c. Scanning electron microscope (SEM) showed that these samples have different surface morphologies. Mössbauer results revealed that the iron exists in different oxidation states (Fe3+, Fe3.5+, and Fe4+ ions) with oxygen vacancies in these samples. X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of Fe3+, Fe4+ ions, and oxygen vacancies at the surface of these samples. The thermal, optical, and magnetic properties of these samples depend on the amount of oxygen deficiency (δ) and the valence states of Fe ions. BaFeO3-δ perovskite samples exhibited antibacterial and antibiofilm activity which can be controlled by the synthesis method. Accordingly, to the present results, the obtained BaFeO3-δ perovskite could be considered as a potential antibacterial and antibiofilm agent.

Review on Sol-Gel Synthesis of Perovskite and Oxide Nanomaterials.

Sol-Gel is a low cost, well-established and flexible synthetic route to produce a wide range of micro- and nanostructures. Small variations in pH, temperature, precursors, time, pressure, atmosphere, among others, can lead to a wide family of compounds that share the same molecular structures. In this work, we present a general review of the synthesis of LaMnO3, SrTiO3, BaTiO3 perovskites and zinc vanadium oxides nanostructures based on Sol-Gel method. We discuss how small changes in the parameters of the synthesis can modify the morphology, shape, size, homogeneity, aggregation, among others, of the products. We also discuss the different precursors, solvents, working temperature, reaction times used throughout the synthesis. In the last section, we present novel uses of Sol-Gel with organic materials with emphasis on carbon-based compounds. All with a perspective to improve the method for future applications in different technological fields.

Symmetric/asymmetric energy storage device of reduced graphene oxide assisted LaNi0.9Co0.1O3 perovskite nanomaterials

Symmetric/asymmetric energy storage device of reduced graphene oxide assisted LaNi0.9Co0.1O3 perovskite nanomaterials

Power-Dependent Photoluminescence Efficiency in Manganese-Doped 2D Hybrid Perovskite Nanoplatelets.

Substitutional metal doping is a powerful strategy for manipulating the emission spectra and excited state dynamics of semiconductor nanomaterials. Here, we demonstrate the synthesis of colloidal manganese (Mn2+)-doped organic-inorganic hybrid perovskite nanoplatelets (chemical formula: L2[APb1-xMnxBr3]n-1Pb1-xMnxBr4; L, butylammonium; A, methylammonium or formamidinium; n (= 1 or 2), number of Pb1-xMnxBr64- octahedral layers in thickness) via a ligand-assisted reprecipitation method. Substitutional doping of manganese for lead introduces bright (approaching 100% efficiency) and long-lived (>500 μs) midgap Mn2+ atomic states, and the doped nanoplatelets exhibit dual emission from both the band edge and the dopant state. Photoluminescence quantum yields and band-edge-to-Mn intensity ratios exhibit strong excitation power dependence, even at a very low incident intensity (<100 μW/cm2). Surprisingly, we find that the saturation of long-lived Mn2+ dopant sites cannot explain our observation. Instead, we propose an alternative mechanism involving the cross-relaxation of long-lived Mn-site excitations by freely diffusing band-edge excitons. We formulate a kinetic model based on this cross-relaxation mechanism that quantitatively reproduces all of the experimental observations and validate the model using time-resolved absorption and emission spectroscopy. Finally, we extract a concentration-normalized microscopic rate constant for band edge-to-dopant excitation transfer that is ∼10× faster in methylammonium-containing nanoplatelets than in formamidinium-containing nanoplatelets. This work provides fundamental insight into the interaction of mobile band edge excitons with localized dopant sites in 2D semiconductors and expands the toolbox for manipulating light emission in perovskite nanomaterials.

STED microscopy reveals in-situ photoluminescence properties of single nanostructures in densely perovskite thin films.

All-inorganic perovskite nanomaterials have attracted much attention recently due to their prominent optical performance and potential application for optoelectronic devices. The carriers dynamics of all-inorganic perovskites has been the research focus because the understanding of carriers dynamics process is of critical importance for improving the fluorescence conversion efficiency. While photophysical properties of excited carrier are usually measured at the macroscopic scale, it is necessary to probe the in-situ dynamics process at the nanometer scale and gain deep insights into the photophysical mechanisms and their localized dependence on the thin-film nanostructures. Stimulated emission depletion (STED) nanoscopy with super-resolution beyond the diffraction limit can directly provide explicit information at a single particle level or nanometer scale. Through this unique technique, we firstly study the in-situ dynamics process of single CsPbBr3 nanocrystals(NCs) and nanostructures embedded inside high-dense samples. Our findings reveal the different physical mechanisms of PL blinking and antibunching for single CsPbBr3 NCs and nanostructures that correlate with thin-film nanostructural features (e.g. defects, grain boundaries and carrier mobility). The insights gained into such nanostructure-localized physical mechanisms are critically important for further improving the material quality and its corresponding device performance.

Stability Enhancements on Methylammonium Lead‐Based Perovskite Nanoparticles: the Smart Use of Host Matrices

AbstractDespite the current advancements, yet improving the intrinsic structure and external environmental stability of hybrid metal halide perovskite nanomaterials is required for developing efficient perovskite‐based devices. Up‐to‐date, a very attractive method is growing and/or embedding perovskite nanocrystals within organic polymeric matrices, or into porous inorganic and hybrid nano/micromaterials (e. g., metal‐organic frameworks, mesoporous silica, zeolites, and others), favored through confinement effect within the pores. In this review, we highlighted the last two years of research progress on enhancing the stabilization of perovskite nanoparticles based on methylammonium cations. In the future generation of optoelectronic and photovoltaic devices along with other interesting applied fields, it is predicted that an effective way to trigger the widespread use of this type of perovskite nanocrystals may involve combining different functional host materials, acting as a smarter protection method for the guest nanocrystals.

High-performance of LaCoO3/Co3O4 nanocrystal as anode for lithium-ion batteries

In order to solve the problem of low capacity and volume expansion of LaCoO3, LaCoO3/Co3O4 perovskite composites were effectively fabricated by a simple hydrothermal method coupled with calcination process. When the calcination temperature is 800 °C, due to the nanoscale sizes, mesoporous structure and heterogeneous components, the samples (named LaCoO3/Co3O4-800) exhibit excellent lithium storage performance as lithium ion batteries (LIBs) anodes. LaCoO3/Co3O4-800 anode exhibits a high reversible capacity (549.7 mAh/g after 100 cycles at 100 mA/g) and superior cycling stability (396.7 mAh/g after 1000 cycles at 1 A/g). This research provides potential candidates for perovskite lanthanide nanomaterials for LIBs anodes.

Enhancing the Intrinsic Activity and Stability of Perovskite Cobaltite at Elevated Temperature Through Surface Stress.

Perovskite-based oxides attract great attention as catalysts for energy and environmental devices. Nanostructure engineering is demonstrated as an effective approach for improving the catalytic activity of the materials. The mechanism for the enhancement, nevertheless, is still not fully understood. In this study, it is demonstrated that compressive strain can be introduced into freestanding perovskite cobaltite La0.8 Sr0.2 CoO3- δ (LSC) nanofibers with sufficient small size. Crystal structure analysis suggests that the LSC fiber is characterized by compressive strain along the ab plane and less distorted CoO6 octahedron compared to the bulk powder sample. Accompanied by such structural changes, the nanofiber shows significantly higher oxygen reduction reaction (ORR) activity and better stability at elevated temperature, which is attributed to the higher oxygen vacancy concentration and suppressed Sr segregation in the LSC nanofibers. First-principle calculations further suggest that the compressive strain in LSC nanofibers effectively shortens the distance between the Co 3d and O 2p band center and lowers the oxygen vacancy formation energy. The results clarify the critical role of surface stress in determining the intrinsic activity of perovskite oxide nanomaterials. The results of this work can help guide the design of highly active and durable perovskite catalysts via nanostructure engineering.

Tunable one-dimensional inorganic perovskite nanomeshes library for water splitting

Perovskites are highly promising candidates in future energy conversion and storage due to their rich diversities and readily tunable electronic properties. However, the poor morphology controllability and limited surface areas have severely limited their applications. We present a generalizable synthesis strategy to fabricate a library of one-dimensional (1D) inorganic perovskite nanomeshes via pyrolysis of metal salt-polymer fibers. Within the evaluated perovskite nanomeshes, La 0.5 Ba 0.5 Co 0.8 Ni 0.2 O 3 delivers the most remarkable performance for the oxygen evolution reaction (OER). Combined X-ray absorption spectroscopy experiments and density functional theory calculations reveal that introduction of additional metals endows more flexible electronic structures to realize the electron transfer in 1D perovskite nanomeshes. This work demonstrates a scalable and retrosynthetic route to easily synthesize the inorganic perovskite nanomaterials with tunable compositions. • Establish the multicomponent 1D perovskite nanomesh library up to six dissimilar metal elements. • The optimized La 0.5 Ba 0.5 Co 0.8 Ni 0.2 O 3 (LBCNO) exhibits a superior OER performance than most reported perovskites. • Demonstrate a scalable and retrosynthetic route to perovskite nanomaterials with tunable composition.

Study the oxygen vacancies and Fe oxidation states in CaFeO3-δ perovskite nanomaterial

CaFeO3-δ perovskite nanomaterial has been synthesized by sol-gel method. Rietveld analysis of the X-Ray diffraction (XRD) data of the CaFeO3-δ sample revealed orthorhombic perovskite structure (space group pcmn). Field emission scanning electron microscope (FE-SEM) of the CaFeO3-δ sample showed the agglomerations of various particles. Mössbauer measurement of the CaFeO3-δ sample showed that the value of δ is 0.262 and Fe oxidation states are Fe3+ in octahedral and Fe4+ in tetrahedral coordination. X-ray photoelectron spectroscopy (XPS) revealed that the presence of Fe3+, Fe4+ ions, and oxygen vacancies at the surface of the CaFeO3-δ sample. Thermogravimetry analysis (TG) and differential scanning calorimetric (DSC) of the CaFeO3-δ sample revealed the presence of phase transitions. The magnetic properties of the CaFeO3-δ sample exhibit mainly antiferromagnetic state as confirmed by Mössbauer measurement. Based on the obtained results, the presence of oxygen vacancies and mixed oxidation states of iron (Fe3+ and Fe4+) makes the CaFeO3-δ sample useful for industrial applications.

Investigations on caesium-incorporated rubidium tin chloride-defect perovskite nanomaterial as highly efficient ultraviolet photocatalysts

Investigations on caesium-incorporated rubidium tin chloride-defect perovskite nanomaterial as highly efficient ultraviolet photocatalysts

An ultrathin two-dimensional iridium-based perovskite oxide electrocatalyst with highly efficient {001} facets for acidic water oxidation

The oxygen evolution reaction (OER) is an electrochemical bottleneck half-reaction in some important energy conversion systems (e.g., water splitting), which is traditionally mediated by iridium oxides in acidic environment. Perovskite-structured Ir-containing oxides (e.g., SrIrO3) are a family of striking electrocatalysts due to their high specific activity, but this excellent quality is difficultly transferred to a nano-electrocatalyst with large active surface and good structural stability. Here, we present a synthesis method that produces a 2D ultrathin {001}-faceted SrIrO3 perovskite (2D-SIO) with a thickness of ∼5 nm and high surface area (57.6 m2 g−1). We show that 2D-SIO can serve as a highly active and stable electrocatalytic nanomaterial for OER under acidic conditions. This perovskite nanomaterial produces 10 mA cm−2 current density at a low overpotential (η, 243 mV), and maintains its catalytic activity after 5000 continuous cyclic measurements. Besides ultrathin structure and large surface area, the exposed {001} facets are found to be the most crucial and unique structural factor for achieving high catalytic activity and structural stability. Our joint experimental and theoretical results demonstrate that these advantageous microstructural features of 2D-SIO endow it with a strong capability to generate the key O* intermediates, and thereby facilitate O–O bond formation and the OER.