Role of self-assembled molecules’anchoring groups for surface defect passivation and dipole modulation in inverted perovskite solar cells

Inverted perovskite solar cells have gained prominence in industrial advancement due to their easy fabrication,low hysteresis effects,and high stability.Despite these advantages,their efficiency is currently limited by excessive defects and poor carrier transport at the perovskite-electrode interface,particularly at the buried interface between the perovskite and transparent conductive oxide(TCO).Recent efforts in the perovskite community have focused on designing novel self-assembled molecules(SAMs)to improve the quality of the buried interface.However,a notable gap remains in understanding the regulation of atomic-scale interfacial properties of SAMs between the perovskite and TCO interfaces.This understanding is crucial,particularly in terms of identifying chemically active anchoring groups.In this study,we used the star SAM([2-(9H-carbazol-9-yl)ethyl]phosphonic acid)as the base structure to investigate the defect passivation effects of eight common anchoring groups at the perovskite-TCO interface.Our findings indicate that the phosphonic and boric acid groups exhibit notable advantages.These groups fulfill three key criteria:they provide the greatest potential for defect passivation,exhibit stable adsorption with defects,and exert significant regulatory effects on interface dipoles.Ionized anchoring groups exhibit enhanced passivation capabilities for defect energy levels due to their superior Lewis base properties,which effectively neutralize local charges near defects.Among various defect types,iodine vacancies are the easiest to passivate,whereas iodine-substituted lead defects are the most challenging to passivate.Our study provides comprehensive theoretical insights and inspiration for the design of anchoring groups in SAMs,contributing to the ongoing development of more efficient inverted perovskite solar cells.

Exploring the role of iron in Fe_(5)Ni_(4)S_(8)toward oxygen evolution through modulation of electronic orbital occupancy

Ni-Fe-based catalysts are considered to be among the most active catalysts for the oxygen evolution reaction(OER)under alkaline conditions,with Fe playing a crucial role.However,Fe leaching occurs during the reaction due to thermodynamic instability,which has resulted in conflicting reports within the literature regarding its role.To clarify this point,we propose a strategy consisting of modulating the electronic orbital occupancy to suppress the extensive loss of Fe atoms during the OER process.Theoretical calculations,in-situ X-ray photoelectron spectroscopy,molecular dynamics simulations,and a series of characterization showed that the stable presence of Fe not only accelerates the electron transfer process but also optimizes the reaction barriers of the oxygen evolution intermediates,promoting the phase transition of Fe_(5)Ni_(4)S_(8)to highly active catalytic species.The modulated Fe_(5)Ni_(4)S_(8)-based pre-catalysts exhibit improved OER activity and long-term durability.This study provides a novel perspective for understanding the role of Fe in the OER process.

The design and engineering strategies of metal tellurides for advanced metal-ion batteries

Owning various crystal structures and high theoretical capacity,metal tellurides are emerging as promising electrode materials for high-performance metal-ion batteries(MBs).Since metal telluride-based MBs are quite new,fundamental issues raise regarding the energy storage mechanism and other aspects affecting electrochemical performance.Severe volume expansion,low intrinsic conductivity and slow ion diffusion kinetics jeopardize the performance of metal tellurides,so that rational design and engineering are crucial to circumvent these disadvantages.Herein,this review provides an in-depth discussion of recent investigations and progresses of metal tellurides,beginning with a critical discussion on the energy storage mechanisms of metal tellurides in various MBs.In the following,recent design and engineering strategies of metal tellurides,including morphology engineering,compositing,defect engineering and heterostructure construction,for high-performance MBs are summarized.The primary focus is to present a comprehensive understanding of the structural evolution based on the mechanism and corresponding effects of dimension control,composition,electron configuration and structural complexity on the electrochemical performance.In closing,outlooks and prospects for future development of metal tellurides are proposed.This work also highlights the promising directions of design and engineering strategies of metal tellurides with high performance and low cost.

Influence of Local Cation Order on Electronic Structure and Optical Properties of Cation-Disordered Semiconductor AgBiS_(2)

Site disorder exists in some practical semiconductors and can significantly impact their intrinsic properties both beneficially and detrimentally.However,the uncertain local order and structure pose a challenge for experimental and theoretical research.Especially,it hinders the investigation of the effects of the diverse local atomic environments resulting from the site disorder.We employ the special quasi-random structure method to perform first-principles research on connection between local site disorder and electronic/optical properties,using cationdisordered AgBiS_(2)(rock salt phase)as an example.We predict that cation-disordered AgBiS_(2)has a bandgap ranging from 0.6 to 0.8 eV without spin-orbit coupling and that spin-orbit coupling reduces this by approximately 0.3 eV.We observe the effects of local structural features in the disordered lattice,such as the one-dimensional chain-like aggregation of cations that results in formation of doping energy bands near the band edges,formation and broadening of band-tail states,and the disturbance in the local electrostatic potential,which significantly reduces the bandgap and stability.The influence of these ordered features on the optical properties is confined to alterations in the bandgap and does not markedly affect the joint density of states or optical absorption.Our study provides a research roadmap for exploring the electronic structure of site-disordered semiconductor materials,suggests that the ordered chain-like aggregation of cations is an effective way to regulate the bandgap of AgBiS_(2),and provides insight into how variations in local order associated with processing can affect properties.

Negative Poisson's Ratios of Layered Materials by First-Principles High-Throughput Calculations

Auxetic two-dimensional(2D)materials,known from their negative Poisson's ratios(NPRs),exhibit the unique property of expanding(contracting)longitudinally while being laterally stretched(compressed),contrary to typical materials.These materials offer improved mechanical characteristics and hold great potential for applications in nanoscale devices such as sensors,electronic skins,and tissue engineering.Despite their promising attributes,the availability of 2D materials with NPRs is limited,as most 2D layered materials possess positive Poisson's ratios.In this study,we employ first-principles high-throughput calculations to systematically explore Poisson's ratios of 40 commonly used 2D monolayer materials,along with various bilayer structures.Our investigation reveals that BP,GeS and GeSe exhibit out-of-plane NPRs due to their hinge-like puckered structures.For 1T-type transition metal dichalcogenides such as M X_(2)(M=Mo,W;X=S,Se,Te)and transition metal selenides/halides the auxetic behavior stems from a combination of geometric and electronic structural factors.Notably,our findings unveil V_(2)O_(5) as a novel material with out-of-plane NPR.This behavior arises primarily from the outward movement of the outermost oxygen atoms triggered by the relaxation of strain energy under uniaxial tensile strain along one of the in-plane directions.Furthermore,our computations demonstrate that Poisson's ratio can be tuned by varying the bilayer structure with distinct stacking modes attributed to interlayer coupling disparities.These results not only furnish valuable insights into designing 2D materials with a controllable NPR but also introduce V_(2)O_(5) as an exciting addition to the realm of auxetic 2D materials,holding promise for diverse nanoscale applications.

Enhancing water-dissociation kinetics and optimizing intermediates adsorption free energy of cobalt phosphide via high-valence Zr incorporating for alkaline water electrolysis

Developing high-efficiency electrocatalysts for hydrogen evolution reaction(HER) and oxygen evolution reaction(OER) is required to enhance the sluggish kinetics of water dissociation and optimize the adsorption free energy of reaction intermediates.Herein,we tackle this challenge by incorporating high-valence Zr into CoP(ZrxCo_(1-x)P),which significantly accelerates the elementary steps of water electrolysis.Theoretical calculations indicate that the appropriate Zr incorporation effectively expedites the sluggish H2O dissociation kinetics and optimizes the adsorption energy of reaction intermediates for boosting the alkaline water electrolysis.These are confirmed by the experimental results of Zr_(0.06)Co_(0.94)P catalyst that delivers exceptional electrochemical activity.The overpotentials at the current density of 10 mA cm^(-2)(j10) are only 62(HER) and 240 mV(OER) in alkaline media.Furthermore,the Zr_(0.06)Co_(0.94)P/CC‖Zr_(0.06)Co_(0.94)P/CC system exhibits superior overall water splitting activity(1.53 V/j10),surpassing most of the reported bifunctional catalysts.This high-valence Zr incorporation and material design methods explore new avenues for realizing high-performance non-noble metal electrocatalysts.

Ultrathin origami accordion-like structure of vacancy-rich graphitized carbon nitride for enhancing CO_(2) photoreduction

Retaining the ultrathin structure of two-dimensional materials is very important for stabilizing their catalytic performances.However,aggregation and restacking are unavoidable,to some extent,due to the van der Waals interlayer interaction of two-dimensional materials.Here,we address this challenge by preparing an origami accordion structure of ultrathin twodimensional graphitized carbon nitride(oa-C_(3)N_(4))with rich vacancies.This novel structured oa-C_(3)N_(4) shows exceptional photocatalytic activity for the CO_(2) reduction reaction,which is 8.1 times that of the pristine C_(3)N_(4).The unique structure not only prevents restacking but also increases light harvesting and the density of vacancy defects,which leads to modification of the electronic structure,regulation of the CO_(2) adsorption energy,and a decrease in the energy barrier of the carbon dioxide to carboxylic acid intermediate reaction.This study provides a new avenue for the development of stable highperformance two-dimensional catalytic materials.

Structure-catalytic functionality of size-facet-performance in pentlandite nanoparticles

As one of the pentlandites,Fe5Ni4S8(FNS) based materials have attracted increasing attention due to their excellent catalytic properties and promising applicability.The control over the catalyst surface structure often benefits its heterogeneous catalytic activity.However,this has not been investigated for FNS materials at the nanoscale regarding the catalytic activity related to high-index facets.Herein,FNS nanoparticles(FNSNPs) with enclosed continuous tunable high-index facets were prepared and studied to clarify the relationship between the structure and catalytic functionality.The results suggested strong dependence between exposed facets of FNSNPs and their sizes.The decline in the average size to5.8 nm led to enclosing by high-index facets(422) and(511) to yield optimal electrocatalytic activities toward the hydrogen evolution reaction.The catalytic activity of FNSNPs was closely related to the surface energy of the main exposed facets.These findings clarified the relationship between high-index-facet and high-surface-energy FNSNPs,as promising approaches in crystal surface control engineering.

Enhanced reconstruction of Fe_(5)Ni_(4)S_(8) by implanting pyrrolidone to unlock efficient oxygen evolution

During oxygen evolution reaction(OER),complex changes have been reported on surfaces of bimetallic Fe-Ni-based catalysts,and regulating the dynamic evolution could improve their electrocatalytic performances.Herein,a pyrrolidone-promoted reconstruction of pentlandite was investigated to uncover the correlation between the reconstructed surface and the OER performance.The theoretical calculations indicated the preferential implantation of pyrrolidone at Fe atoms,useful for regulating the electronic structures of pentlandite.The vale nce state of Ni increased,suggesting the promotion of the in-situ reconstruction of pentlandite via strengthening hydroxyl adsorption to generate highly active NiOOH.The electron-rich pentlandite was also found conducive to charge transfer under applied voltages.The Operando Raman and various quasi-in-situ characterizations confirmed the realization of more delocalized electronic structures of pentlandite by introducing pyrrolidone.This,in turn,promoted the accumulation of hydroxyl groups on the pentlandite surface,thereby boosting the formation of highly active NiOOH at lower OER potentials.Consequently,the adsorption energies of intermediates were optimized,conducive to enhanced OER reaction kinetics.As a proof of concept,the pentlandite decorated by pyrrolidone exhibited an overpotential as low as 265 mV at 10 mA cm^(-2) coupled with stable catalysis for 1000 hours at a high current density of 100 mA cm^(-2).In sum,new insights into unlocking the high catalytic activity of bimetallic Fe-Ni-based catalysts were provided,promising for future synthesis of advanced catalysts.

Moiré superlattices arising from growth induced by screw dislocations in layered materials

Moiré superlattices(MSLs) are modulated structures produced from homogeneous or heterogeneous two-dimensional layers stacked with a twist angle and/or lattice mismatch. Enriching the methods for fabricating MSL and realizing the unique emergent properties are key challenges in its investigation. Here we recommend that the spiral dislocation driven growth is another optional method for the preparation of high quality MSL samples. The spiral structure stabilizes the constant out-of-plane lattice distance, causing the variations in electronic and optical properties. Taking SnS_(2) MSL as an example, we find prominent properties including large band gap reduction(~ 0.4 e V) and enhanced optical activity. Firstprinciples calculations reveal that these unusual properties can be ascribed to the locally enhanced interlayer interaction associated with the Moiré potential modulation. We believe that the spiral dislocation driven growth would be a powerful method to expand the MSL family and broaden their scope of application.

Evaluation of performance of machine learning methods in mining structure-property data of halide perovskite materials

With the rapid development of artificial intelligence and machine learning(ML)methods,materials science is rapidly entering the era of data-driven materials informatics.ML models serve as the most crucial component,closely bridging material structure and material properties.There is a considerable difference in the prediction performance of different ML methods for material systems.Herein,we evaluated three categories(linear,kernel,and nonlinear methods)of models,with twelve ML algorithms commonly used in the materials field.In addition,halide perovskite was chosen as an example to evaluate the fitting performance of different models.We constructed a total dataset of 540 halide perovskites and 72 features,with formation energy and bandgap as target properties.We found that different categories of ML models show similar trends for different target properties.Among them,the difference between the models is enormous for the formation energy,with the coefficient of determination(R2)range 0.69-0.953.The fitting performance between the models is closer for bandgap,with the R^(2)range 0.941-0.997.The nonlinear-ensemble model shows the best fitting performance for both the formation energy and the bandgap.It shows that the nonlinear-ensemble model,constructed by combining multiple weak learners,effectively describes the nonlinear relationship between material features and target property.In addition,the extreme gradient boosting decision tree model shows the most superior results among all the models and searches for two new descriptors that are crucial for formation energy and bandgap.Our work provides useful guidance for the selection of effective machine learning methods in the data-mining studies of specific material systems.

Revealing the Intrinsic Peroxidase-Like Catalytic Mechanism of Heterogeneous Single-Atom Co-MoS2

The single-atom nanozyme is a new concept and has tremendous prospects to become a next-generation nanozyme.However,few studies have been carried out to elucidate the intrinsic mechanisms for both the single atoms and the supports in single-atom nanozymes.Herein,the heterogeneous single-atom Co-MoS2(SA Co-MoS2)is demonstrated to have excellent potential as a high-performance peroxidase mimic.Because of the well-defined structure of SA Co-MoS2,its peroxidase-like mechanism is extensively interpreted through experimental and theoretical studies.Due to the different adsorption energies of substrates on different parts of SA Co-MoS2 in the peroxidase-like reaction,SA Co favors electron transfer mechanisms,while MoS2 relies on Fenton-like reactions.The different catalytic pathways provide an intrinsic understanding of the remarkable performance of SA Co-MoS2.The present study not only develops a new kind of single-atom catalyst(SAC)as an elegant platform for understanding the enzyme-like activities of heterogeneous nanomaterials but also facilitates the novel application of SACs in biocatalysis.

High-throughput computational material screening of the cycloalkane-based two-dimensional Dion–Jacobson halide perovskites for optoelectronics

Two-dimensional(2D) layered perovskites have emerged as potential alternates to traditional three-dimensional(3D)analogs to solve the stability issue of perovskite solar cells. In recent years, many efforts have been spent on manipulating the interlayer organic spacing cation to improve the photovoltaic properties of Dion–Jacobson(DJ) perovskites. In this work, a serious of cycloalkane(CA) molecules were selected as the organic spacing cation in 2D DJ perovskites, which can widely manipulate the optoelectronic properties of the DJ perovskites. The underlying relationship between the CA interlayer molecules and the crystal structures, thermodynamic stabilities, and electronic properties of 58 DJ perovskites has been investigated by using automatic high-throughput workflow cooperated with density-functional(DFT) calculations.We found that these CA-based DJ perovskites are all thermodynamic stable. The sizes of the cycloalkane molecules can influence the degree of inorganic framework distortion and further tune the bandgaps with a wide range of 0.9–2.1 eV.These findings indicate the cycloalkane molecules are suitable as spacing cation in 2D DJ perovskites and provide a useful guidance in designing novel 2D DJ perovskites for optoelectronic applications.

Global instability index as a crystallographic stability descriptor of halide and chalcogenide perovskites

Crystallographic stability is an important factor that affects the stability of perovskites.The stability dictates the commercial applications of lead-based organometal halide perovskites.The tolerance factor(t)and octahedral factor(μ)form the state-of-the-art criteria used to evaluate the perovskite crystallographic stability.We studied the crystallographic stabilities of halide and chalcogenide perovskites by exploring an effective alternative descriptor,the global instability index(GII)that was used as an indicator of the stability of perovskite oxides.We particularly focused on determining crystallographic reliability by calculating GII.We analyzed the bond valence models of the 243 halide and chalcogenide perovskites that occupied the lowest-energy cubic-phase structures determined by conducting the first-principles-based total energy minimization calculations.The decomposition energy(ΔHD)reflects the thermodynamic stability of the system and is considered as the benchmark that helps assess the effectiveness of GII in evaluating the crystallographic stability of the systems under study.The results indicated that the accuracy of predicting thermodynamic stability was significantly higher when GII(73.6%)was analyzed compared to the cases when t(55%)andμ(39.1%)were analyzed to determine the stability.The results obtained from the machine learning-based data mining method further indicate that GII is an important descriptor of the stability of the perovskite family.

Magnetic Field Effect on Critical Behavior of Perovskite Ferromagnet

The polycrystalline samples of La2/3Ca1/3MnO3 were prepared by a conventional solid state reaction method. The magnetizations （ZFC, FC and initial magnetization） of the polycrystalline La2/3Ca1/3MnO3 were measured with superconducting quantum interference device magnetometer. The scaling theory was employed to study the changes of critical behavior arising from the applied external field. The critical parameter β decreases with increasing the external magnetic field results in an increase in the magnitude of ferromagnetic ordering.

Strong interactions in molybdenum disulfide heterostructures boosting the catalytic performance of water splitting: A short review

Two-dimensional materials(2DMs) have attracted substantial attention due to their abundant active sites and their ultrahigh surface area for different catalytic applications due to the high lateral-longitudinal ratio. Transition metal dichalcogenides(TMDs), especially MoS2, as one of the 2DMs most often studied, have shown superior activity in electrochemical applications. Recently, combinations of different 2DMs have been widely studied, and they appear to be the most promising strategy available to develop state of the art catalysts for different reactions.In this article, we review the interactions between MoS2 and other materials as well as the novel assembly induced phase transitions of TMDs and their underlying mechanisms. Several methods for inducing the phase transition of TMDs by building MoS2-based heterostructures have been introduced. The electronic coupling between these counterparts has significantly enhanced their conductivity and optimized the energy states of the materials, thus introducing enhanced activity as compared to their original counterparts. The ideas summarized in this article may shed new light on and help to develop next-generation green energy materials by designing and constructing highly active two-dimensional catalysts for efficient water splitting.

Temperature-induced phase transition of two-dimensional semiconductor GaTe

GaTe is a two-dimensional Ⅲ-Ⅵ semiconductor with suitable direct bandgap of~1.65 eV and high photoresponsivity,which makes it a promising candidate for optoelectronic applications.GaTe exists in two crystalline phases:monoclinic(m-GaTe,with space group C2/m) and hexagonal(h-GaTe,with space group P63/mmc).The phase transition between the two phases was reported under temperature-varying conditions,such as annealing,laser irradiation,etc.The explicit phase transition temperature and energy barrier during the temperature-induced phase transition have not been explored.In this work,we present a comprehensive study of the phase transition process by using first-principles energetic and phonon calculations within the quasi-harmonic approximation framework.We predicted that the phase transition from h-GaTe to m-GaTe occurs at the temperature decreasing to 261 K.This is in qualitative agreement with the experimental observations.It is a two-step transition process with energy barriers 199 meV and 288 meV,respectively.The relatively high energy barriers demonstrate the irreversible nature of the phase transition.The electronic and phonon properties of the two phases were further investigated by comparison with available experimental and theoretical results.Our results provide insightful understanding on the process of temperature-induced phase transition of GaTe.

Superior Mechanical Properties of GaAs Driven by Lattice Nanotwinning

Gallium arsenide(GaAs),a typical covalent semiconductor,is widely used in the electronic industry,owing to its superior electron transport properties.However,its brittle nature is a drawback that has so far significantly limited its application.An exploration of the structural deformation modes of GaAs under large strain at the atomic level,and the formulation of strategies to enhance its mechanical properties is highly desirable.The stressstrain relations and deformation modes of single-crystal and nanotwinned GaAs under various loading conditions are systematically investigated,using first-principles calculations.Our results show that the ideal strengths of nanotwinned GaAs are 14% and 15% higher than that of single-crystal GaAs under pure and indentation shear strains,respectively,without producing a significantly negative effect in terms of its electronic performance.The enhancement in strength stems from the rearrangement of directional covalent bonds at the twin boundary.Our results offer a fundamental understanding of the mechanical properties of single crystal GaAs,and provide insights into the strengthening mechanism of nanotwinned GaAs,which could prove highly beneficial in terms of developing reliable electronic devices.

Theoretical design of diamondlike superhard structures at high pressure

Diamond, as the hardest known material, has been widely used in industrial applications as abrasives, coatings, and cutting and polishing tools, but it is restricted by several shortcomings, e.g., its low thermal and chemical stability. Considerable efforts have been devoted to designing or synthesizing the diamond-like B-C-N-O compounds, which exhibit excellent mechanical property. In this paper, we review the recent theoretical design of diamond-like superhard structures at high pressure. In particular, the recently designed high symmetric phase of low-energy cubic BC3 meets the experimental observation, and clarifies the actual existence of cubic symmetric phase for the compounds formed by B-C-N-O system,besides the classical example of cubic boron nitride.

Kinetically and thermodynamically expediting elementary steps via high-valence Cr-incorporated of nickel selenide for water electrolysis

Designing high-performance electrocatalysts toward hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)is essential to reduce the activation barrier and optimize free adsorption energy of reactive intermediates.Herein,we report that incorporating high-valence Cr into NiSe_(2)(Cr_(x)Ni_(1-x)Se_(2))kinetically and thermodynamically expedites elementary steps of both HER and OER.The as-prepared Cr_(0.05)Ni_(0.95)Se_(2) catalyst displays excellent HER and OER activities,with low overpotentials of 89 and 272 mV at the current density of 10 mA·cm^(-2)(j10),respectively,and remains stable during operation for 30 h.A low cell voltage of only 1.59 V is required to drive j10 in alkaline media.In situ Raman spectroscopy reveals that Cr incorporation facilitates the formation of NiOOH active species during the OER process.Meanwhile,theoretical explorations demonstrate that high-valence Cr incorporation efficiently accelerates water dissociation kinetics and improves H*adsorption during HER process,lowering the activation barrier of OER and optimizing the adsorption energy of oxygen-based intermediate,thus kinetically and thermodynamically enhancing the intrinsic performance of NiSe_(2) for over water splitting.This strategy provides a new horizon to design transition metal based electrocatalysts in the clean energy field.