Perovskite Composition Research Articles

Origin and redox conditions of the Rosário-6 alnöite of southern Brazil: Implications for the state of the mantle during Gondwana breakup

The Rosário-6 alnöite is an alkaline occurrence that belongs to the Rosário do Sul kimberlitic field, situated in the south-eastern edge of the Paraná Basin, in the South of Brazil, and erupted concomitant or just after the volcanism of the Paraná-Etendeka Large Igneous Province (LIP). Following recent published nomenclature, Rosário-6 was classified as a kimberlite from a deep mantle source with a distinctive inequigranular texture resulting from the presence of olivine macrocrysts set in a finer-grained matrix. Trace element compositions of olivine, monticellite, spinel, phlogopite, perovskite and apatite show an enrichment of Nb, Ce, Ta and U, which implies that the Rosário-6 mantle source was enriched by recycled oceanic crust. The positive anomalies of Rb, Ba and Sr, the enrichment in LREE, and the negative anomalies of HREE in the Rosário-6 minerals, are indicative of a metasomatic process in the mantle source that could be caused by fluids from recycled oceanic crust. Temperature, pressure and redox conditions (fO2) of Rosário-6 crystallization are estimated from olivine, spinel, perovskite and monticellite compositions: Rosário-6 crystallization temperatures using olivine-spinel geothermobarometry were around 1390(±56)°C at a pressure of 2 GPa, and 1405(±56)°C at 3 GPa with ΔNNO = 2.8, at pressures constrained by the silica activity limited by the crystallization of monticellite. Using a perovskite oxybarometer, we obtained a larger range of ΔNNO (from −2.8 to 3.4), whereas the monticellite oxybarometer results in fO2 of −2.6 to −0.8 ΔNNO units. The fO2 indicate that the mantle source of Rosário-6 at the time of crystallization was possibly oxidized by materials from ancient subduction, which may be the cause for Rosário-6's low potential to carry and preserve diamonds. Horizontal tomographic images derived from P-wave velocity data constrain the thickness of the lithosphere in this region and the overall information indicates that mantle cooling at depths below 200 km may have resulted of an accumulation of oceanic plate slabs from old subduction. The geochemical data in conjunction with the geophysical characterizes the conditions of Rosário-6 mineral crystallization and also the mantle of this part of South America during Gondwana breakup.

Tuning the electronic levels of NiO with alkali halides surface modifiers for perovskite solar cells

Favorable optoelectronic properties and ease of fabrication make NiO a promising hole transport layer for perovskite solar cells. To achieve maximum efficiency, the electronic levels of NiO need to be optimally aligned with those of the perovskite absorber. Applying surface modifiers by adsorbing species on the NiO surface, is one of the most widespread strategies to tune its energy levels. Alkali halides are simple inorganic surface modifiers that have been extensively used in organic optoelectronics, however, rarely studied in perovskite solar cells. Using density functional theory (DFT) calculations, we investigate the effect of single layer adsorption of twenty different alkali halides on the electronic levels of NiO. Our results show that alkali halides can shift the position of the valence band maximum (VBM) of NiO to a surprisingly large extend in both directions, from -3:10 eV to +1:59 eV. We interpret the direction and magnitude of the shift in terms of the surface dipoles, formed by the adsorbed cations and anions, where the magnitude of the VBM shift is a monotonic function of the surface coverage. Our results indicate that with alkali halide surface modifiers, the electronic levels of NiO can be tuned robustly and potentially match those of many perovskite compositions in perovskite solar cells.

Perovskite-sensitized upconversion bingo: Stoichiometry, composition, solvent, or temperature?

Triplet-triplet annihilation-based photon upconversion (UC) using bulk perovskite sensitizers has been previously shown to facilitate efficient UC at low fluences. However, the fabrication of the UC devices has not been fully optimized; thus, there is room for improvement. Here, we apply techniques that have been successful in enhancing the performance of perovskite solar cells in order to also improve perovskite-sensitized UC devices. In particular, we investigate the use of a post-fabrication thermal annealing step, overstoichiometric vs stoichiometric addition of PbI2 to the perovskite precursors, methylammonium vs formamidinium cation-rich lead halide perovskite compositions, and the use of different solvents for the annihilator molecules on the perovskite/annihilator interface. We find that excess PbI2 does not significantly affect the UC process, while the perovskite composition is crucial for the yield of extracted carriers across the interface. Comparing toluene and chlorobenzene, we find that the solvent used to deposit the annihilator is also a key factor in the overall device performance. Moreover, we find that thermal annealing of the whole device architecture significantly improves the UC performance by a factor of three.

Regulated Crystallization of FASnI3 Films through Seeded Growth Process for Efficient Tin Perovskite Solar Cells

Although rapid progress has been made in tin-based perovskite solar cells (PSCs), the inferior film qualities of the solution-processed perovskites always lead to poor reproducibility and instability. Herein, we present a simple seeded growth (SG) approach to obtain high-quality tin-based perovskite films with preferred crystal orientation, large grain sizes, and fewer apparent grain boundaries. High-quality tin-based perovskite films fabricated through this SG process could greatly reduce the nonradiative recombination centers and inhibit the oxidation of Sn2+. Using formamidinium tin tri-iodide (FASnI3) perovskites, the SG-PSCs exhibit a much improved efficiency from 5.37% (control) to 7.32% with all improved photovoltaic parameters. Moreover, this SG strategy is easily applicable to other tin-based perovskite compositions. The PSC based on methylammonium (MA) doped mixed-cation perovskite (FA0.75MA0.25SnI3) exhibited a power conversion efficiency (PCE) of 8.54% with an improvement of 19.3% in the photovoltaic performance, making it a general approach for achieving efficient tin-based PSCs.

High‐throughput computational design of halide perovskites and beyond for optoelectronics

AbstractHalide perovskites have attracted great interest as promising next‐generation materials in optoelectronics, ranging from solar cells to light‐emitting diodes. Despite their exceptional optoelectronic properties and low cost, the prototypical organic–inorganic hybrid lead halide perovskites suffer from toxicity and low stability. Therefore, it is of high demand to search for stable and nontoxic alternatives to the hybrid lead halide perovskites. Recently, high‐throughput computational materials design has emerged as a powerful approach to accelerate the discovery of new halide perovskite compositions or even novel compounds beyond perovskites. In this review, we discuss how this approach discovers halide perovskites and beyond for optoelectronics. We first overview the background of halide perovskites and methodologies in high‐throughput computational design. Then, we focus on materials properties for different optoelectronic applications, and how they are assessed with materials descriptors. Finally, we review different studies in terms of specific materials types to discuss their design principles, screening results, and experimental verification.This article is categorized under: Structure and Mechanism > Computational Materials Science Electronic Structure Theory > Density Functional Theory

Developing Low-Cost, High Performance, Robust and Sustainable Perovskite Electrocatalytic Materials in the Electrochemical Sensors and Energy Sectors: “An Overview”

Since its discovery in 1839, research on the synthesis and application of perovskite materials has multiplied largely due to their suitability to be used in the fields of nanotechnology, chemistry and material science. Appropriate changes in composition or addition of other elements or blending with polymers may result in new hybrid and/or composite perovskite materials that will be applied in advanced fields. In this review, we have recapitulated the recent progress on perovskite nanomaterial in solar cell, battery, fuel cell and supercapacitor applications, and the prominence properties of perovskite materials, such as excellent electronic, physical, chemical and optical properties. We discussed in detail the synthesis and results of various perovskite hybrid nanomaterials published elsewhere. We have also discussed the results of various studies on these low dimensional composite nanomaterials in broad sectors such as electronics/optoelectronics, batteries, supercapacitors, solar cells and electrochemical sensors.

Создание и получение композиционного вещества лантанилоксалата бария на основе золь-гель технологии

This article explored a method for producing a compound of the type perovskite composition. Ba0.5X×Ox1X (where X=0.5:0.5=1). A multi-component composition was obtained during coagulation and gel formation (xerogel) of pH 5.5, acidic medium, at a temperature of 45–50 °C, mechanical stirring for 10 hours. The sol–gel crystallization of the compound was determined at a temperature of 400–500 °C and the previously obtained substance was named Barium Lanthanyloxalate.

Narrow-Bandgap Mixed Lead/Tin-Based 2D Dion-Jacobson Perovskites Boost the Performance of Solar Cells.

The advent of the two-dimensional (2D) family of halide perovskites and their demonstration in 2D/three-dimensional (3D) hierarchical film structures broke new ground toward high device performance and good stability. The 2D Dion-Jacobson (DJ) phase halide perovskites are especially attractive in solar cells because of their superior charge transport properties. Here, we report on 2D DJ phase perovskites using a 3-(aminomethyl)piperidinium (3AMP) organic spacer for the fabrication of mixed Pb/Sn-based perovskites, exhibiting a narrow bandgap of 1.27 eV and a long carrier lifetime of 657.7 ns. Consequently, solar cells employing mixed 2D DJ 3AMP-based and 3D MA0.5FA0.5Pb0.5Sn0.5I3 (MA = methylammonium, FA = formamidinium) perovskite composites as light absorbers achieve enhanced efficiency and stability, giving a power conversion efficiency of 20.09% with a high open-circuit voltage of 0.88 V, a fill factor of 79.74%, and a short-circuit current density of 28.63 mA cm-2. The results provide an effective strategy to improve the performance of single-junction narrow-bandgap solar cells and, potentially, to give a highly efficient alternative to bottom solar cells in tandem devices.

P‐212: Late‐News‐Poster: Study on the Ideal Structural Change of Perovskite LEDs for Enhanced Performances by Using Different Perovskite Composition

In this study, we compared the effects of two types of perovskite compositions on the efficiency of perovskite LED devices. The perovskite based on methylammonium cation (MA) requires interlayer for efficient device performances and formamidinium cation (FA) showed much better efficiency when we used simpler structure without using any interlayer. To understand those different optimal structure, we proceeded exciton lifetime measurement to confirm exciton quenching processes at the HIL and EML interface.

Co-Evaporated p-i-n Perovskite Solar Cells beyond 20% Efficiency: Impact of Substrate Temperature and Hole-Transport Layer.

For methylammonium lead iodide perovskite solar cells prepared by co-evaporation, power conversion efficiencies of over 20% have been already demonstrated, however, so far, only in n-i-p configuration. Currently, the overall major challenges are the complex evaporation characteristics of organic precursors that strongly depend on the underlying charge selective contacts and the insufficient reproducibility of the co-evaporation process. To ensure a reliable co-evaporation process, it is important to identify the impact of different parameters in order to develop a more detailed understanding. In this work, we study the influence of the substrate temperature, underlying hole-transport layer (polymer PTAA versus self-assembling monolayer molecule MeO-2PACz), and perovskite precursor ratio on the morphology, composition, and performance of co-evaporated p-i-n perovskite solar cells. We first analyze the evaporation of pure precursor materials and show that the adhesion of methylammonium iodide (MAI) is significantly reduced with increased substrate temperature, while it remains almost unaffected for lead iodide (PbI2). This substrate temperature-dependent evaporation behavior of MAI is also transferred to the co-evaporation process and can directly influence the perovskite composition. We demonstrate that the optimal substrate temperature window for perovskite deposition is close to room temperature. At high temperature, not enough MAI for precise stoichiometry is incorporated even with very high MAI rates. While, at temperatures below -25 °C, the conversion of MAI with PbI2 is inhibited, and an amorphous yet unreacted film is formed. We observe that perovskite composition and morphology vary widely between the organic hole-transport layers (HTLs) PTAA and MeO-2PACz. For all substrate temperatures, MeO-2PACz enables higher solar cell PCEs than PTAA. Through the combination of vapor-deposited perovskites and a self-assembled monolayer, we achieve a stabilized power conversion efficiency of 20.6%, which is the first reported PCE above 20% for evaporated perovskite solar cells in p-i-n architecture.

Reduced Self-Doping of Perovskites Induced by Short Annealing for Efficient Solar Modules

Summary Controlling of doping in semiconducting light absorber can minimize the charge recombination and maximizing power output from solar cells; however, it is challenging for perovskites due to lack of controlled doping. Here, we report that a short post-annealing of less than 3 min for facilitating high-throughput manufacturing of perovskite solar modules in an ambient environment maintains the stoichiometric composition of perovskites, encouraging a spontaneous de-doping of perovskites during aging. The reduced self-doping results in less charge recombination and, thus, higher device efficiency. The stabilized open-circuit voltage of sub-cells in the CH3NH3PbI3 minimodules with an area >20 cm2 reaches 1.19 V on average. The aperture efficiency reaches 17.8% under one sun and 18.7% under a quarter sun illumination, deriving an averaged efficiency >20.0% for each sub-cell with an area >3 cm2, demonstrating the excellent uniformity of the films by this scalable process. The minimodule also works as uniform light-emitting devices.

Stabilizing Organic-Inorganic Lead Halide Perovskite Solar Cells With Efficiency Beyond 20.

The power conversion efficiency (PCE) of organic–inorganic lead halide perovskite solar cells (PSCs) has exceeded 25%, approaching the best record of their silicon counterpart. However, lifetime issues still stand between PSCs and the goal of mass commercialization. For instance, most photoactive perovskites are hydrophilic, and moisture can quickly turn some of their constituents to compounds yielding trap states. Some perovskites are not thermally stable in the temperature window of solar cell operation and will transform into photo-inactive non-perovskites. If a perovskite is of an inadequate quality, e.g., vacancies, surface area, or grain boundaries per unit volume are high, there exist more defect sites, acting as migration pathways for perovskite ions under photo-bias, and the migration changes the perovskite's composition. An unstable perovskite/charge transport material (CTM) interface allows cross-contamination between molecules from both sides of the interface. Even without external stress, perovskite ions in an operating PSC undergo redox processes, which create defect states or initiate chemical chain reactions to accelerate PSC degradation. This mini-review discussed recent progress in solving issues, including the above, to stabilize PSCs with competitive PCE beyond 20%. The remarkable longevity of 15 PSCs under accelerated aging tests was probed in depth from three viewpoints: (1) perovskite compositions and dopants, (2) perovskite additives, and (3) CTMs. This mini-review, within which crucial perovskite-stabilizing methods were systematically analyzed, can be used as a quick-start guide when dealing with PSCs' stability in the future.

Halide (Cl/Br)-Incorporated Organic–Inorganic Metal Trihalide Perovskite Films: Study and Investigation of Dielectric Properties and Mechanical Energy Harvesting Performance

Compositional tuning of organic–inorganic metal trihalide perovskites (OTPs) via halide (Cl/Br) incorporation has attracted increased attention due to the rapid advancements in the performance of optoelectronic devices based on mixed halide perovskites. It is expected that the fine-tuning of OTPs can significantly enhance the dielectric and piezoelectric properties that are beneficial for constructing a high-performance piezoelectric nanogenerator (PENG). However, few studies on these aspects have so far been reported. In the present study, mixed halide perovskite thin films with various halide (Cl or Br) contents were fabricated by a simple two-step spin-coating method. The effects of fine-tuning the halide composition of methylammonium lead iodide perovskite (MAPbI3) on the morphological, electrical, dielectric, and piezoelectric properties of the perovskite thin films were systematically investigated. In addition, the feasibility of using these mixed halide-MAPbI3 thin films in mechanical energy-harvesting systems was also thoroughly examined by constructing a series of flexible PENGs. The energy-harvesting performance of the PENG was found to be significantly influenced by the amount of incorporated Cl or Br in the MAPbI3 film. Among all the fabricated PENGs, the 4Cl-MAPbI3 PENG poled at 50 kV/cm exhibited a much higher piezoelectric output performance, with an output voltage of ∼5.9 V and an output current density of ∼0.61 μA/cm2. Thus, the present study demonstrates a simple and reliable method for tuning the dielectric and piezoelectric properties of the OTP materials toward developing flexible, high-performance devices which may offer a wide range of utility in wearable and portable electronic devices.

One-pot synthesis of LaFeO3@C composites for catalytic transfer hydrogenation reactions: Effects of carbon precursors

Carbon encapsulated LaFeO3 perovskite composites (LaFeO3@C) were synthesized by a one-pot method and the effects of carbohydrates as carbon precursor on the activity of LaFeO3@C for catalytic transfer hydrogenation (CTH) reactions were investigated. The textural and surface properties (e.g., pore structure, surface acidity and basicity) of LaFeO3@C vary significantly with carbohydrates, which offer a facile route to tailor the sample by simply changing the carbon precursor. LaFeO3@C-M, using maltose as carbon precursor, shows the best catalyst for the CTH of furfural with isopropanol, with conversion and selectivity of 90.3 % and 94.3 %, respectively, owing to the surface La enrichment, rich oxygen functional groups / oxygen vacancy and matched surface acidity-basicity. This sample is also recyclable after post-treatment in N2 atmosphere and can be applied to catalytic hydrogenation of various carbonyl compounds. The current one-step synthesis method provides an efficient way to design carbon-containing composite catalysts with controllable properties for catalytic applications.

Comprehensive insights into defect passivation and charge dynamics for FA0.8MA0.15Cs0.05PbI2.8Br0.2 perovskite solar cells

Nonradiative charge recombination is the main restriction on the high efficiency of organic–inorganic hybrid perovskite solar cells (PVSCs). The synergistic manipulation of the grain boundary/interface traps can control charge behavior and improve device performance. In our work, the composition of perovskite used is FA0.8MA0.15Cs0.05PbI2.8Br0.2 (MA is methylammonium, FA is formamidinium), which produces high-performing PVSCs. A trace additive of n-butylammonium bromide (BABr) was incorporated into the perovskite precursor to passivate grain–boundary defects. The NH4Cl/KCl was spin-coated onto the electron-transport layer to modify interface contact and impede nonradiative charge recombination, inducing a high power-conversion efficiency (PCE). The highest-performing PVSCs achieved a PCE of 21.02%, a Voc of 1.13 V, a Jsc of 23.55 mA cm−2, and a FF of 0.79 under a reverse voltage scan (under a forward voltage scan the values were as follows: PCE, 20.13%; Voc, 1.12 V; Jsc, 23.65 mA cm−2; FF, 0.76), with a negligible J–V hysteresis. The hybrid 2D/3D perovskite heterostructure formed through the incorporation of BABr increased crystallinity and mitigated nonradiative recombination, resulting in reduced current-voltage hysteresis, enhanced efficiency, and significantly improved operational stability. With impedance spectroscopy and time-resolved surface photovoltage spectroscopy, the charge dynamics in PVSCs were determined.

Understanding the interplay of stability and efficiency in A-site engineered lead halide perovskites

Organic–inorganic hybrid lead halide perovskites have gained significant attention as light-harvesting materials in thin-film photovoltaics due to their exceptional optoelectronic properties and simple fabrication process. The power conversion efficiency of perovskite solar cells (PSCs) has surged beyond 25% in a short time span. Their transition to commercial market is a “work in progress” due to limited long-term operational stability and the persisting environmental concern due to the presence of lead. Comprehensive investigations on the interplay of material composition and interfacial effects on the device performance of PSCs based on methylammonium lead iodide have shown the crucial role of an A-site cation in incipient deterioration of the material through external stimuli (moisture, light, oxygen, or heat). Consequently, a partial or complete replacement of A-site cations by up to four isoelectronic substituents has resulted in many new perovskite compositions. The correlations between the chemical composition and the optoelectronic properties are, however, not always easy to determine. A-site cation management is governed by stability and charge neutrality of the lattice, and the choices include Cs+-cations and organic cations such as CH3NH3+ or CH(NH2)2+ and combinations thereof. Since the size of the cations is an important structural parameter, an adequate compositional engineering of the A-site could effectively optimize the stability by reducing non-radiative defect sites and enhancing carrier lifetimes. This Perspective reflects on the experimental strategies for A-site cation management and their direct impact on the stability and device performance. It also highlights the opportunities and challenges for further research and industrial commercialization of PSCs.

Halide Perovskites – Optoelectronic and Structural Characterization Methods

Halide Perovskites – Optoelectronic and Structural Characterization Methods

Efficient and Reproducible Monolithic Perovskite/Organic Tandem Solar Cells with Low-Loss Interconnecting Layers

Summary Perovskite solar cells (PSCs) and organic photovoltaics (OPVs) have both undergone rapid development recently. The composition and molecular tunability of perovskite and organic semiconductors enable a large material pool with different band gaps and various physical characters, giving feasibility to construct perovskite/organic tandem solar cells (TSCs). Here, we developed a semi-empirical model, rationally selected the best available material combination, and successfully demonstrated the efficient and reproducible TSCs benefiting from their complementary band gaps and orthogonal processing solvents. Featuring with all-thermally evaporated low-loss interconnecting layers (ICLs), our 2-termimal (2T) monolithic perovskite/organic TSCs deliver high reproducibility with power conversion efficiency (PCE) narrowly distributed between 20% and 20.6% (certified as 19.54%). In addition to the promising efficiency, the UV sensitivity of OPVs is eliminated in the tandem structure, demonstrating its advantage on device stability. Those results unfold significant potentials of perovskite/organic tandem devices as reproducible and cost-effective structures to achieve high-performance TSCs.

Nano-Micro Dimensional Structures of Fiber-Shaped Luminous Halide Perovskite Composites for Photonic and Optoelectronic Applications.

Perovskite nanomaterials have been revealed as highly luminescent structures regarding their dimensional confinement. In particular, their promising potential lies behind remarkable luminescent properties, including color tunability, high photoluminescence quantum yield, and the narrow emission band of halide perovskite (HP) nanostructures for optoelectronic and photonic applications such as lightning and displaying operations. However, HP nanomaterials possess such drawbacks, including oxygen, moisture, temperature, or UV lights, which limit their practical applications. Recently, HP-containing polymer composite fibers have gained much attention owing to the spatial distribution and alignment of HPs with high mechanical strength and ambient stability in addition to their remarkable optical properties comparable to that of nanocrystals. In this review, the fabrication methods for preparing nano-microdimensional HP composite fiber structures are described. Various advantages of the luminescent composite nanofibers are also described, followed by their applications for photonic and optoelectronic devices including sensors, polarizers, waveguides, lasers, light-down converters, light-emitting diode operations, etc. Finally, future directions and remaining challenges of HP-based nanofibers are presented.

Easy Strategy to Enhance Thermal Stability of Planar PSCs by Perovskite Defect Passivation and Low-Temperature Carbon-Based Electrode.

Organic-inorganic lead halide perovskite has recently emerged as an efficient absorber material for solution process photovoltaic (PV) technology, with certified efficiency exceeding 25%. The development of low-temperature (LT) processing is a challenging topic for decreasing the energy payback time of perovskite solar cell (PSC) technology. In this context, the LT planar n-i-p architecture meets all the requirements in terms of efficiency, scalability, and processability. However, the long-term stability of the LT planar PSC under heat and moisture stress conditions has not been carefully assessed. Here, a detailed study on thermal and moisture stability of large-area (1 cm2) LT planar PSCs is presented. In particular, the key role in thermal stability of potassium iodide (KI) insertion in the perovskite composition is demonstrated. It is found that defect passivation of triple-cation perovskite by KI doping inhibits the halide migration induced by thermal stress at 85 °C and delays the formation of degradation subproducts. T80, defined as the time when the cell retains 80% of initial efficiency, is evaluated both for reference undoped devices and KI-doped ones. The results show that T80 increases 3 times when KI doping is used. Moreover, an HTL-free architecture where the Au top electrode is replaced with low-T screen-printable carbon paste is proposed. The combination of the carbon-based HTL-free architecture and KI-doped perovskite permits T80 to increase from 40 to 414 h in unsealed devices.