Perovskite Composition Research Articles

Rapid Interlayer Charge Separation and Extended Carrier Lifetimes due to Spontaneous Symmetry Breaking in Organic and Mixed Organic-Inorganic Dion-Jacobson Perovskites.

Promising alternatives to three-dimensional perovskites, two-dimensional (2D) layered metal halide perovskites have proven their potential in optoelectronic applications due to improved photo- and chemical stability. Nevertheless, photovoltaic devices based on 2D perovskites suffer from poor efficiency owing to unfavorable charge carrier dynamics and energy losses. Focusing on the 2D Dion-Jacobson perovskite phase that is rapidly rising in popularity, we demonstrate that doping of complementary cations into the 3-(aminomethyl)piperidinium perovskite accelerates spontaneous charge separation and slows down charge recombination, both factors improving the photovoltaic performance. Employing ab initio nonadiabatic (NA) molecular dynamics combined with time-dependent density functional theory, we demonstrate that cesium doping broadens the bandgap by 0.4 eV and breaks structural symmetry. Assisted by thermal fluctuations, the symmetry breaking helps to localize electrons and holes in different layers and activates additional vibrational modes. As a result, the charge separation is accelerated. Simultaneously, the charge carrier lifetime grows due to shortened coherence time between the ground and excited states. The established relationships between perovskite composition and charge carrier dynamics provide guidelines toward future material discovery and design of perovskite solar cells.

Synthesis and Characterization of Impurity‐Free Li6/16Sr7/16Ta3/4Hf1/4O3 Perovskite as a Solid‐State Lithium‐Ion Conductor

Perovskite‐type lithium‐ion conductors are a potential class of solid‐state electrolytes for solid‐state batteries due to their excellent environmental stability, good mechanical strength, reasonably wide electrochemical stability window, and high ionic conductivity. A‐site deficient Li6/16Sr7/16Ta3/4Hf1/4O3 is a promising perovskite composition identified, but it is prone to form impurity phases during synthesis, which introduces high grain bounary resistance to the total ionic conductivity. A systematic investigation is reported on the effect of the synthesis conditions (e.g., excess Li, sintering temperature, and mother powder protection) on the phase composition and properties of this perovskite. The results show that the mother powder bed protection and 1450 °C sintering temperature without Li compensation are the best conditions to achieve single phase. The single‐phase sample exhibits 96% theoretical density, a bulk ionic conductivity of 0.408 mS cm−1, and an electronic conductivity of 3.6 × 10−9 S cm−1 at 25 °C with an activation energy of 0.352 eV, Young's modulus of 63.91 GPa, and shear modulus of 26.16 GPa. However, Li6/16Sr7/16Ta3/4Hf1/4O3 is unstable against lithium metal and can be reduced readily. Alternative anode materials or surface protection layers are needed if it is considered as an electrolyte for lithium‐metal based solid‐state lithium‐ion batteries.

Heterojunction built sillenite/ perovskite (Bi25Fe2O39-SrTiO3) composite of distinct light sensitive nature for an interactive solar photocatalysis performance

In the present study a heterojunction was built in between visible light and UV light sensitive materials (Bi25Fe2O39/SrTiO3) of sillenite and perovskite nature with varied Bismuth ferrite (BFe) loading on fixed SrTiO3 (STO). The predominance of sillenite phase (Bi25Fe2O39) in the bulk of bismuth iron oxide was confirmed through diffraction and XPS analysis. The as obtained composites resulted in an improved crystal characteristic, in terms of increased crystal size and reduced lattice strain. Several locations in the FESEM and HRTEM images revealed formation of interface between BFe and STO. The shifting of binding energies for the elements further supported the formation of the heterojunction features. The band energy for composites was reduced to greater extent with low charge-carrier recombination. The solar photocatalytic degradation of Bisphenol A (BPA) demonstrated a highest removal efficiency (∼95 %) and apparent quantum efficiency (1.75 ×10−2) for B 1.5 S composite. The optimum crystal packing between BFe/STO had significant contribution for the band formation and prompted charge transfer between the built-in junction interfaces through a type II heterojunction charge transfer mechanism. The photocatalysis of the BPA was predominately driven by the ⁕O2- radical. The obtained ferromagnetic characteristics of the composite (B 1.5 S: 0.0742 emu/g (Mr), 15.013 Oe (Hc)) revealed ease separation of the photocatalyst from the liquid stream.

Reducing nonradiative recombination in perovskite solar cells with a porous insulator contact.

Inserting an ultrathin low-conductivity interlayer between the absorber and transport layer has emerged as an important strategy for reducing surface recombination in the best perovskite solar cells. However, a challenge with this approach is a trade-off between the open-circuit voltage (Voc) and the fill factor (FF). Here, we overcame this challenge by introducing a thick (about 100 nanometers) insulator layer with random nanoscale openings. We performed drift-diffusion simulations for cells with this porous insulator contact (PIC) and realized it using a solution process by controlling the growth mode of alumina nanoplates. Leveraging a PIC with an approximately 25% reduced contact area, we achieved an efficiency of up to 25.5% (certified steady-state efficiency 24.7%) in p-i-n devices. The product of Voc × FF was 87.9% of the Shockley-Queisser limit. The surface recombination velocity at the p-type contact was reduced from 64.2 to 9.2 centimeters per second. The bulk recombination lifetime was increased from 1.2 to 6.0 microseconds because of improvements in the perovskite crystallinity. The improved wettability of the perovskite precursor solution allowed us to demonstrate a 23.3% efficient 1-square-centimeter p-i-n cell. We demonstrate here its broad applicability for different p-type contacts and perovskite compositions.

Giant dielectric response and grain heterogeneity of Y2/3Cu3Ti4O12–TiO2 composite ceramics fabricated by hydrothermal process

AbstractDue to the boom of the electronic information industry, dielectric ceramic materials are widely applied in passive components such as multilayer ceramic capacitors. In this article, Y2/3Cu3Ti4O12–TiO2 composite ceramics with outstanding dielectric properties (εr = 2.29 × 106 at 20 Hz, εr = 4.49×105 at 1 kHz) were successfully prepared by hydrothermal and in situ solid‐state methods. The minimum dielectric loss value (at 1 kHz) of the obtained composite ceramics is about 0.57. The experimental results show that Y2/3Cu3Ti4O12 has a composite perovskite structure with cation vacancies, which causes internal electron‐pinned defect‐dipole, and the easy entry of excessive titanium ions to produce donor defects. Meanwhile, the heterogeneous grains with a pomegranate‐like microstructure were observed in the prepared composite ceramics, and interfacial polarization between subgrain boundaries was substantiated by impedance analysis. The abundant weakly trapped electrons and more polarized interfaces formed by grain and subgrain boundaries are the primary sources of the excellent dielectric properties of composite ceramics.

Additive engineering for highly efficient and stable perovskite solar cells

Since the groundbreaking report on solid-state perovskite solar cells (PSCs) in 2012, PSC receives great attention due to its high power conversion efficiency (PCE) obtainable at low-cost fabrication. A PCE of 9.7% in 2012 was swiftly improved to 25.7% in 2022 via perovskite composition engineering and grain size control. The excellent photovoltaic performance originates from the defect-tolerant property of organic lead halide perovskite associated with the antibonding nature of the valence band. Nevertheless, the reduction of defect-induced trap density of the state is still required to improve further photovoltaic performance and stability. Among the methods reported to reduce defects, additive engineering is one of the promising strategies for controlling crystallographic defects because it can regulate crystallization kinetics and grain boundaries. In this review, we describe materials and methods for additive engineering applied to lead-based perovskite. In addition, the effects of additive engineering on photovoltaic performance and stability are discussed.

Solar-driven photocatalytic transformation of toluene to benzoic acid over perovskite-type NiTiO3 decorated with reduced GO and g-C3N4 nanosheets

In this work, a perovskite-type nickel (II) titanate (NiTiO3; labeled as NTO) was synthesized and supported with reduced graphene oxide (rGO) and graphitic carbon nitride (CN: g-C3N4) nanosheets by ultrasound-assisted impregnation method. The solar-induced photocatalytic activity and selectivity of the prepared NTO-based perovskite catalysts were evaluated for toluene (TOL) oxidation to benzoic acid (B_COOH) under varying operating conditions. Results revealed that the NTO perovskite exhibited a higher selectivity (95–98%) for the photooxidation of TOL to B_COOH by 125–95 times higher than benzaldehyde (B_CHO) and benzyl alcohol (B_CH2OH) at 1 vol% H2O2 and O2 flow. At zero H2O2 level, the selective oxidation of TOL to B_CHO and B_CH2OH enhanced by 5.4 and 2.7 times as compared with the B_COOH production rate. Besides, NTO@CN (NTN) outperformed NTO@rGO (NTG) for the selective photocatalytic oxidation of TOL to B_COOH in solvent-free and water media under UV, visible, and sunlight irradiation. The production yield of B_COOH was 388.4, 491.2, and 455.6 µmol/L over NTO, NTN, and NTG, respectively at 1 vol% H2O2 and O2 flow for 3 h of solar irradiation. In both composites, carbon sheets supported the photocatalytic stability of NTO and potential energy for H2O2 decomposition to ∙OH radicals. This is validated by the radical scavenger test and electron paramagnetic resonance (EPR) analysis, which verified the crucial role of hydroxyl (•OH) radicals in the photocatalytic oxidation of TOL to B_COOH. These findings proved the effectiveness of NTN and NTG perovskite composites for solar-induced organic synthesis of benzoic acid from water contaminated with toluene using sunlight (as a renewable energy source).

Development for Highly Efficient Organometal Halide Perovskite Solar Cells and Modules

Organometal halide perovskites have captured wide interest as a promising material for light-weight and high-efficiency solar cells. Through recent studies of the organometal halide perovskite solar cells (PSCs), the composition of organometal halide perovskites is recognized as one of the key factors in the improvement of the PCE. In this study, we investigated mixed cation perovskite absorber. Additionally, we successfully constructed monolithic PSC mini-module without I-V hysteresis. In the case of MA-free PSCs, the 24.9% PCE (0.187 cm2) and 21.6% PCE (2.76 cm2 monolithic PSC mini-module) were obtained, respectively. We also developed semitransparent perovskite top cells with higher durability and transmittance for tandem solar cells. The PCEs of 19.5% (certified 19.3%) and 26.2% were achieved for a 1 cm2 semi-transparent perovskite top cell and four-terminal PSC/CIGS tandem solar cells, respectively.

Hoisting photovoltaic performance of perovskite BaSnO3 nanoparticles wrapped reduced graphene oxide: Efficient photoelectrode for dye-sensitized solar cell

Inorganic perovskite nanostructure photoanode has a very important role in dye-sensitized solar cells (DSSC),in collecting photogenerated electrons coming from dye sensitizer. The photo-electric-conversion efficiency of photoelectrode is hindered by an effective photogenerated electron hole/pair. To avoid this problem, modification of BaSnO3 perovskite nanoparticles with graphene nanosheets is attempted in our work. Facile one-step synthesis of RGO loaded BaSnO3 (RGO-BaSnO3 NC) was done by simple solution route. As-prepared perovskite composite was studied using characterization techniques namely Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM) and field emission scanning electron microscopy (FE-SEM). The photovoltaic performances of RGO-BaSnO3 NC-based photoanode in DSSC employing N719 dye, Pt-counter electrode and imidazole-based liquid electrolyte have been studied under standard simulated lighting of 100 mW cm−2. It was found that RGO-BaSnO3 NC showed better dye adsorption to facilitate light harvesting and promoted a proficient electron transport pathway owing to fewer electron trapping sites on the surface than the pristine BaSnO3 NPs surface. The results demonstrate that the fabricated DSSC made with RGO-BNC-based photoanode delivered overall photoelectric conversion efficiency of 5.59 %, which is 32 % higher than that of DSSC fabricated unmodified BaSnO3 photoanode.

Distributed Feedback Lasers by Thermal Nanoimprint of Perovskites Using Gelatin Gratings.

To date, thermal nanoimprint lithography (NIL) for patterning hybrid perovskites has always involved an intricate etching step of a hard stamp material or its master. Here, we demonstrate for the first time the successful nanopatterning of a perovskite film by NIL with a low-cost polymeric stamp. The stamp consists of a dichromated gelatin grating structured by holographic lithography. The one-dimensional grating is imprinted into a perovskite film at 95 °C and 90 MPa for 10 min, resulting in a high quality second-order distributed feedback (DFB) laser. The laser exhibits an excellent performance with a threshold of 81 μJ/cm2, a line width of 0.32 nm, and a pronounced linear polarization. This novel approach enables cost-effective fabrication of high-quality DFB lasers compatible with different perovskite compositions and photonic nanostructures for a wide range of applications.

Understanding thermochemical energy storage performance of Ba1-xSrxCoO3-δ perovskite system: A computational and experimental study

Concentrated solar power coupled with thermochemical energy storage (TCES) has emerged as an effective approach for renewable energy utilization. TCES based on perovskites attracts much attention because of temperature tunability and high flexibility. In this work, the electronic structures are simulated by the density functional theory (DFT) method, revealing the reduction temperatures is related to the formation energy of oxygen vacancy (Evac). The compounds of Ba1-xSrxCoO3-δ with x = 0–1 are synthesized and investigated by experimental methods. According to the results, Ba content improves the redox capacities and reaction kinetics, while Sr content expands the reaction temperatures and enhances the micro morphologies. In addition, all the samples present a greater reversibility after 150 cycles, because the extended pores are beneficial to the oxygen diffusion. Overall, Ba0.5Sr0.5CoO3-δ is suggested as a suitable TCES material with a reaction enthalpy of 202.20 kJ kg−1. This study provides a design principle of composite perovskites for thermochemical energy storage.

Charge transport in mixed metal halide perovskite semiconductors.

Investigation of the inherent field-driven charge transport behaviour of three-dimensional lead halide perovskites has largely remained challenging, owing to undesirable ionic migration effects near room temperature and dipolar disorder instabilities prevalent specifically in methylammonium-and-lead-based high-performing three-dimensional perovskite compositions. Here, we address both these challenges and demonstrate that field-effect transistors based on methylammonium-free, mixed metal (Pb/Sn) perovskite compositions do not suffer from ion migration effects as notably as their pure-Pb counterparts and reliably exhibit hysteresis-free p-type transport with a mobility reaching 5.4 cm2 V-1 s-1. The reduced ion migration is visualized through photoluminescence microscopy under bias and is manifested as an activated temperature dependence of the field-effect mobility with a low activation energy (~48 meV) consistent with the presence of the shallow defects present in these materials. An understanding of the long-range electronic charge transport in these inherently doped mixed metal halide perovskites will contribute immensely towards high-performance optoelectronic devices.

In-situ fabricated and plasmonic enhanced MACsPbBr3-polymer composite perovskite film based UV photodetector

Organic-inorganic hybrid perovskite is being extensively applied to optoelectronics. However, the complex fabrication techniques, long-term instability, inefficient charge transportation; poor surface coverage hinders the expansion of its applications. Herein, we report for the first time the in-situ synthesis of MACsPbBr3-perovskite crystals in polymer-matrix to act as a light absorber for efficient ultraviolet light detection. The devices fabricated with the MACsPbBr3-perovskite films showed a maximum photocurrent of 8.9 × 10−6, a dark current of 1.7 × 10−11 A, responsivity of 45.75 AW−1, detectivity of 1.05 × 1013 Jones and on/off ratio >105 at 0 V, under the illumination of 0.28 mW cm−2. The plasmonic enhancement was explored by fabricating PDs on (gold nanoparticles) AuNPs/ZnO structure, which exhibited photocurrent enhancement (10−5), ascribed to the huge localized electric field induced by the surface plasmon resonance, scattering, and reflectance from AuNPs and structured ZnO surface, and improved the responsivity (55.91 AW−1) and on/off ration (>106) by 1.12-fold and 10-fold. And the formed Schottky barrier between Pero and AuNPs/ZnO region could lead to the reduced dark current (10−13 A) and improved detectivity (7.91 × 1014 Jones). This study offers a different pathway for the designing of high-performance plasmonic PDs.

Influence of synthesis conditions on the physicochemical and electrocatalytic properties of non-stoichiometric Ba2Sr2La2Ti4O12 perovskites

Present work studies the influence of the pretreatment milling media (deionized water (BLTOS-H) and isopropanol (BLTOS-i)) on the surface characteristics, structure, chemical composition and catalytic activity of non-stoichiometric Ba2Sr2La2Ti4O12 perovskites. The IR spectroscopy and XRD analyses shows a difference in the structure and phase composition of the two materials. X-ray photoelectron spectroscopy detects a Ba2+- and La3+-enriched and Sr2+-depleted surface. The BLTOS-i sample appears to exhibit higher specific surface area (SSA) and pore volume in comparison to BLTOS-H. The electrochemical tests showed that BLTOS-H sample have similar behavior to platinum at current densi-ties up to 10 mA cm-2, while BLTOS-i presented highest electrochemical performance among all tested samples over the entire current range.

Blade Coating Inverted Perovskite Solar Cells with Vacuum‐Assisted Nucleation Based on Bottom Quasi‐2D Passivation

Metal halide perovskite solar cells (PSCs) attract an enormous attention because of their high power conversion efficiency (PCE) and low fabrication cost. However, their commercialization is limited by fabricating highly efficient large‐area solar cells. Controlling the morphology and crystallization of perovskite for large‐area fabrication is difficult but important. Herein, a vacuum‐assisted approach is developed to obtain mirror‐like, pinhole‐free, highly crystalline, and uniform blade‐coated perovskite films, without the use of antisolvent and air knife. This method can be a universal approach for various perovskite compositions. Meanwhile, the phenethylammonium iodide passivation effect at the top and bottom interfaces of perovskite layer based on FTO/NiOx/perovskite/C60/BCP/Cu inverted p‐i‐n structure is systematically investigated. The optimized device fabricated by blade coating under an ambient environment exhibits the champion PCE of 20.7% and is among the top few records of blade coating inverted structure based on NiOx hole transport layer. The encapsulated device retains 97% of its maximum efficiency under open‐circuit condition after 1000 h of photostability test in an ambient environment at room temperature with a relative humidity of 40–60%. Herein, low‐cost, easy, and reproducible strategies to fabricate efficient and stable blade‐coated PSCs are demonstrated.

Research Progress of Ba(Zn1/3Nb2/3)O3 Microwave Dielectric Ceramics: A Review

Ba(Zn1/3Nb2/3)O3 (BZN) microwave dielectric ceramics have attracted great attention due to their high-quality factor (Q), near-zero temperature coefficient of resonant frequency (τf), and suitable dielectric constant (εr), making them promising materials for application in microwave devices. Due to their superior dielectric properties, composite perovskite ceramics are widely used in the field of microwave communication, base stations, navigation, radar, etc. This article summarized the latest research progress of BZN ceramics and discusses the main preparation methods and performance modifications. Furthermore, the problems faced by BZN ceramics and solutions to improve their performance, as well as their potential applications, are analyzed. This article provides a reference for the design and preparation of BZN ceramics.

Barium cerate and its composite perovskites – synthesis techniques: a comprehensive review

Perovskites have attracted growing interest in recent eras due to their unique properties and potential applications. Barium cerate (BC) proton-conducting perovskites have been examined over decades for various applications such as hydrogen sensors, fuel cells, proton separation membranes, etc. When compared with oxide ion conductors under the same circumstances, ceramic proton conducting barium cerate can diminish the working temperature of solid oxide fuel cells to an intermediate temperature range, 673–873 K because of their higher ionic conduction. The present review carefully analyses and summarizes different synthesis approaches with optimization conditions to prepare BC-derived perovskites and the reported data have been carefully analyzed. A range of synthesis methods such as solid-state reaction method and wet chemical processes like coprecipitation, combustion, Pechini method, etc., have been systematically investigated. Even though the solid-state method has considerable disadvantages, most researchers avoid its incompetence due to the easiness of processing. Applications of the material have been briefly deliberated to exemplify its technological importance. The present review concluded with the recent signs of progress and innovative techniques employed to overcome the processing complications in these materials.

How fast do defects migrate in halide perovskites: insights from on-the-fly machine-learned force fields.

The migration of defects plays an important role in the stability of halide perovskites. It is challenging to study defect migration with experiments or conventional computer simulations. The former lacks an atomic-scale resolution and the latter suffers from short simulation times or a lack of accuracy. Here, we demonstrate that machine-learned force fields, trained with an on-the-fly active learning scheme against accurate density functional theory calculations, allow us to probe the differences in the dynamical behaviour of halide interstitials and halide vacancies in two closely related compositions CsPbI3 and CsPbBr3. We find that interstitials migrate faster than vacancies, due to the shorter migration paths of interstitials. Both types of defects migrate faster in CsPbI3 than in CsPbBr3. We attribute this to the less compact packing of the ions in CsPbI3, which results in a larger motion of the ions and thus more frequent defect migration jumps.

Ultrasmall water-stable CsPbBr3 quantum dots with high intensity blue emission enabled by zeolite confinement engineering.

Ultrasmall CsPbBr3 perovskite quantum dots (PQDs) as promising blue-emitting materials are highly desired for full-color display and lighting applications, but their inferior efficiency and poor ambient stability hinder extensive applications. Herein, a "break-and-repair" strategy has been developed to tightly confine monodispersed ultrasmall CsPbBr3 PQDs in a zeolite. In this strategy, the CsPbBr3 PQDs are introduced into the zeolite via a high temperature evaporation method, wherein the perovskite precursors break the zeolite framework, and amino acids and silane are then used to fix the damaged framework and lock the perovskite QDs within the matrix. By modulating the synthetic conditions to control the growth of CsPbBr3, PQDs with ultrasmall size of 2 nm have been obtained in the zeolite, giving emission centered at 460 nm with a high quantum yield of 76.93%. Strikingly, the PQDs@zeolite composite exhibits water-induced reversible photoluminescence promoted by the coordination between the amino acids and PQDs in a dynamic manner, achieving enhanced water stability (14 days in aqueous solution). This work provides a new perspective for the synthesis of water-stable blue-emitting perovskite composites for potential applications in lighting fields.

Temperature and frequency dependent dielectric and electrical properties of relaxor (Ca1/2W1/2)(Pb1/2Ni1/2)O3 electronic material

In the present study, a solid-state reaction technique is used to formulate and synthesize the (Ca0.5W0.5)(Pb0.5Ni0.5)O3, [CWPN] relaxor perovskite composite. Its structural, morphological, and electrical characteristics have all been revealed so that they may be studied for potential use in electronics and sensors. X-ray diffraction analyses have confirmed the structure to be combination of primary tetragonal along with secondary rhombohedral and orthorhombic phase. Throughout a wide temperature and frequency range (25° – 500° C and 1 kHz–1 MHz), the impedance spectroscopy, dielectric, and a.c. conductivity have all been analyzed. The sample's dielectric spectroscopy confirmed its relaxor properties. On a Nyquist plot, the sample's grain contribution is represented by a single semicircular arc. A replica of a similar circuit was constructed so that its electrical characteristics could be studied. Both the activation energy and the mobility of the charge carriers have been evaluated. Conducting systematic studies of dielectric properties at elevated temperatures is crucial for fundamental characterization and device development, as it allows for the analysis of electrical parameters associated with surfaces, grain borders, or grains.