Efficient and stable planar all-inorganic perovskite solar cells based on high-quality CsPbBr3 films with controllable morphology

All-inorganic cesium lead bromide(CsPbBr3)perovskite is attracting growing interest as functional materials in photovoltaics and other optoelectronic devices due to its superb stability.However,the fabrication of high-quality CsPbBr3 films still remains a big challenge by solution-process because of the low solubility of the cesium precursor in common solvents.Herein,we report a facile solution-processed approach to prepare high-quality CsPbBr3 perovskite films via a two-step spin-coating method,in which the Cs Br methanol/H2 O mixed solvent solution is spin-coated onto the lead bromide films,followed by an isopropanol-assisted post-treatment to regulate the crystallization process and to control the film morphology.In this fashion,dense and uniform CsPbBr3 films are obtained consisting of large crystalline domains with sizes up to microns and low defect density.The effectiveness of the resulting CsPbBr3 films is further examined in perovskite solar cells(PSCs)with a simplified planar architecture of fluorine–doped tin oxide/compact Ti O2/CsPbBr3/carbon,which deliver a maximum power conversion efficiency of 8.11%together with excellent thermal and humidity stability.The present work offers a simple and effective strategy in fabrication of high-quality CsPbBr3 films for efficient and stable PSCs as well as other optoelectronic devices.

Surfactant-assisted hydrothermally synthesized MoS_2 samples with controllable morphologies and structures for anthracene hydrogenation

MoS_2 samples with controllable morphologies and structures were synthesized using surfactantassisted hydrothermal processes.The effects of surfactants（PEG,PVP,P123,SDS,AOT,and CTAB）on the morphologies and structures of MoS_2 samples were investigated.The results revealed that spherical,bulk-like,and flower-like MoS_2 particles assembled by NH4~＋-intercalated MoS_2 nano-sheets were synthesized.The morphologies of the MoS_2 samples and their structures（including the slab length and the number of stacked layers） of MoS_2 nano-sheets in these samples could be controlled by adjusting the surfactants.Mono-dispersed spherical MoS_2 particles could be synthesized with PEG via the creation of MoS_2 nano-sheets with slab lengths shorter than 15 nm and fewer than six stacked layers.Possible formation mechanisms of these MoS_2 samples created via surfactant-assisted hydrothermal processes are proposed.Further,the catalytic activities of MoS_2 samples for anthracene hydrogenation were evaluated in a slurry-bed reactor.The catalyst synthesized with the surfactant PEG exhibited the highest catalytic hydrogenation activity.Compared with the other catalysts,it had a smaller particle size,mono-dispersed spherical morphology,shorter slab length,and fewer stacked layers;these were all beneficial to exposing its active edges.This work provides an efficient approach to synthesize transition metal sulfides with controllable morphologies and structures.

Morphology control of aluminum nitride(AlN)for a novel high-temperature hydrogen sensor

Hydrogen is a promising renewable energy source for fossil-free transportation and electrical energy generation.However,leaking hydrogen in high-temperature production processes can cause an explosion,which endangers production workers and surrounding areas.To detect leaks early,we used a sensor material based on a wide bandgap aluminum nitride(AlN)that can withstand a high-temperature environment.Three unique AlN morphologies(rod-like,nest-like,and hexagonal plate-like)were synthesized by a direct nitridation method at 1400℃usingγ-AlOOH as a precursor.The gas-sensing performance shows that a hexagonal plate-like morphology exhibited p-type sensing behavior and showed good repeatability as well as the highest response(S=58.7)toward a 750 ppm leak of H2 gas at high temperature(500°C)compared with the rod-like and nest-like morphologies.Furthermore,the hexagonal plate-like morphology showed fast response and recovery times of 40 and 82 s,respectively.The surface facet of the hexagonal morphology of AlN might be energetically favorable for gas adsorption–desorption for enhanced hydrogen detection.

Three-dimensionally oriented organization of hexagonal MIL-96 microplates toward superior film microstructure

Preferential orientation control of metal—organic framework(MOF)films is advantageous for maximizing pore uniformity and minimizing grain-boundary defects.Nonetheless,the preparation of MOF films with both in-plane and out-of-plane orientations remains a grand challenge.In this study,we reported the preparation of three-dimensionally oriented MIL-96 layers through combining morphology control of MIL-96 seeds with addition of polyvinylpyrrolidone surfactants and arachidonic acids.The three-dimensionally oriented MIL-96 film was readily obtained through in-plane epitaxial growth.It is anticipated that the aforementioned protocol can be effective for obtaining diverse MOF films with a three-dimensionally oriented organization.

Polymer Fiber Rigid Network with High Glass Transition Temperature Reinforces Stability of Organic Photovoltaics

Organic photovoltaics(OPVs)need to overcome limitations such as insufficient thermal stability to be commercialized.The reported approaches to improve stability either rely on the development of new materials or on tailoring the donor/acceptor morphology,however,exhibiting limited applicability.Therefore,it is timely to develop an easy method to enhance thermal stability without having to develop new donor/acceptor materials or donor–acceptor compatibilizers,or by introducing another third component.Herein,a unique approach is presented,based on constructing a polymer fiber rigid network with a high glass transition temperature(T_(g))to impede the movement of acceptor and donor molecules,to immobilize the active layer morphology,and thereby to improve thermal stability.A high-T_(g) one-dimensional aramid nanofiber(ANF)is utilized for network construction.Inverted OPVs with ANF network yield superior thermal stability compared to the ANF-free counterpart.The ANF network-incorporated active layer demonstrates significantly more stable morphology than the ANF-free counterpart,thereby leaving fundamental processes such as charge separation,transport,and collection,determining the device efficiency,largely unaltered.This strategy is also successfully applied to other photovoltaic systems.The strategy of incorporating a polymer fiber rigid network with high T_(g) offers a distinct perspective addressing the challenge of thermal instability with simplicity and universality.

Morphology Control of Anatase TiO2 by Surfactant-assisted Hydrothermal Method

By hydrolysing titanium isopropoxide in a long hydrocarbon chain surfactant-containing solution, TiO2 fine particles with a diversity of well-defined morphologies was synthesized in this study by a hydrothermal route. The structural change during the formation process was monitored by scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. TiO2 with various morphologies such as particle, sheet, rod, tube and flower-like shape was obtained by carefully controlling the preparation conditions. The experimental results show that the pH value is crucial for shape control of the produced TiO2 because it can change the charge state of the surfactant in the solution and the adsorption potential of the surfactant on the TiO2 surface. The shape evolvement of anatase TiO2 was elucidated by quenching the reaction at different stage and the formation mechanism of different shaped TiO2 was suggested.

Morphology Control of SrCO_3 Crystals using Complexons as Modifiers in the Ethanol-water mixtures

Using SrC12-6H2O and Na2CO3 as the main raw materials and adding different complexons as modifiers with simple co-precipitation method, SrCO3 crystals with distinct morphologies like spherical, bundle-like, overlapping plate-like, hexagonal star-like, dumbbell-like, etc. can be synthesized in the ethanol-water mixtures. The samples were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and Fourier transform infrared spectrograph （FT-IR）. The interrelated effect mechanism is presented in the end. Results show that the modifier carboxyl groups play a significant role in controlling the SrCO3 crystal morphologies, which can alter the crystal growth unit （Sr^2＋） supply mode and induce the crystal formation with the morphologies matching their spatial configurations.

Morphology control of ultrafine cuprous oxide powder and its growth mechanism

Four shapes of Cu2O particles as sphere,cube,truncated octahedron and octahedron were prepared via glucose reduction of Cu(Ⅱ)under alkaline condition.The products were characterized by XRD and SEM.The effects of the precursor(CuO,Cu(OH)2), reaction temperature and glucose concentration on morphology of Cu2O particles were investigated,and the mechanism of morphology control was discussed on the basic theory of crystal nucleation and growth.It is found that the Cu+supersaturation is remarkably influenced by the precursor kind,reaction temperature and glucose concentration,and the morphology of Cu2O particles can be controlled by the Cu+supersaturation.

A systematic correlation between morphology of porous carbon cathode and electrolyte in lithium-sulfur battery

Porous carbon has been applied for lithium-sulfur battery cathodes,and carbonized metal-organic framework(MOF)is advantageous in tuning the morphology.Herein,we have systematically synthesized water-distorted MOF(WDM)derived porous carbon via controlling the proportion of both water in a mixed solvent(dimethylformamide and water)and ligand in MOF-5 precursors(metal and ligand),which is categorized by its morphology(i.e.Cracked stone(closed),Tassel(open)and Intermediate(semi-open)).For example,decrease in water and increase in ligand content induce Cracked stone WDMs which showed the highest specific surface area(2742-2990 m^(2)/g)and pore volume(2.81-3.28 cm^(3)/g)after carbonization.Morphological effect of carbonized WDMs(CWDMs)on battery performance was examined by introducing electrolytes with different sulfur reduction mechanisms(i.e.DOL/DME and ACN_(2) LiTFSITTE):Closed framework effectively confines polysulfide,whereas open framework enhances electrolyte accessibility.The initial capacities of the batteries were in the following order:Cracked stone>Intermediate>Tassel for DOL/DME and Intermediate>Tassel>Cracked stone for ACN_(2) LiTFSI-TTE.To note,Intermediate CWDM exhibited the highest initial capacity and retained capacity after 100 cycles(1398 and 747 mAh/g)in ACN_(2) LiTFSI-TTE electrolyte having advantages from both open and closed frameworks.In sum,we could correlate cathode morphology(openness and pore structure)and electrolyte type(i.e.polysulfide solubility)with lithium-sulfur battery performance.

Effect of OHˉ on morphology of Cu_2O particles prepared through reduction of Cu(Ⅱ) by glucose

Cu2O particles with different shapes were prepared via reducing Cu（II） in alkaline system by glucose at 50℃. The products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. It is found that the shape of Cu2O particles changes with the change of concentration of NaOH. The different shapes of Cu2O particles are due to the absorption of OH- ions on Cu2O particles, which arise the variety of growth mode of Cu2O, and then influence the morphology of Cu2O particles.

Planar morphology and controlling factors of the gullies in the Yuanmou Dry-hot Valley based on field investigation

The plane form of a gully can provide a basis for evaluating the gully volume and erosion rate, acting process, and evolutionary stage. For describing the planar characteristics of a permanent gully and understanding their controlling factors, this study, utilizing a total station and GPS RTK, measured the shoulder lines and channel curves of 112 gullies in six sites of the Yuanmou Dry-hot Valley and then mapped them by Arc GIS software and calculated nine parameters. The results showed that the channel lengths range from 10.88 to 249.11 m; the widths range from 6.20 to 40.99 m; the perimeters range from 54.11 to 541.67 m; the gully areas range from 153.02 to 6,930.30 m2; the left-side areas range from 92.93 to 4,027.20 m2; and the right-side areas range from 63.65 to 3,539.77 m2. The slightly sinuous and straight gullies account for 73.21% of the total gullies; the quantity of the right skewed gullies is 8.93% greater than that of the left skewed ones based on the symmetry ratio; the shape ratios range from 1.12 to 1.40 and the morphology ratios from 0.038 to 1.294; the fractal dimension is 1.192. Gullies in different sites have diverse planar characteristics. Except for the symmetry index, which was close to a negatively skewed distribution, all of the other parameters had the characteristic of positively skewed distribution. The gully area is related to the length and width, but the gully length has a weak correlation with the width. The evolutionary stage, topographic conditions, strata, soil properties, and piping erosion played very important roles in the gully planar morphology. This study could provide useful information for controlling gully erosion and safeguarding human habitation and engineering buildings.

Influence of EDTA on the Morphology of Barium Carbonate Using High Gravity Technology

The superfine BaCO3 particles were synthesized by high gravity technology with BaCl·2H2O and Na2CO3 as the raw materials. The changes of particle size and morphology were studied by adding different amount of EDTA, and rod-like, near-spherical and cylindrical shape BaCO3 were prepared. The BaCO3 particles were analyzed and characterized by TG/SDAT, SEM, XRD and FT-IR. The results indicated that the crystal transformation temperature and decomposition temperature of BaCO3 had increased because of EDTA addition. With the increase of EDTA amount, the shape of BaCO3 changed from irregular rod-like to near-spherical then to cylindrical shape. All different shape BaCO3 adopts orthorhombic crystal systems.

Facile and controllable synthesis of BaCO_3 crystals superstructures using a CO_2-storage material

We here report a new CO_2 capture and storage method that converts CO_2 into a novel alkyl carbonate salt, denoted as CO_2 SM, by a system consisting of equimolar 1,4-butanediol(BDO) and 1,2-ethylenediamine(EDA). This novel CO_2 SM was then used to prepare BaCO_3 crystals through a simple and fast hydrothermal synthesis under mild conditions. The CO_2 SM was both the source of CO_2 and the modifier to regulate the nucleation and growth of BaCO_3 crystals. The morphology of the BaCO_3 crystals could be tuned from rod to shuttle by adjusting the key influencing factors, including CO_2 SM concentration, mineralization temperature, and mineralization time. A possible mechanism for the synthesis of BaCO_3 crystals from the CO_2 SM was also presented. After the BaCO_3 crystals were isolated, the filtrate of the hydrothermal reaction could be recycled to again absorb CO_2 and prepare BaCO_3 crystals of the same polymorph. This novel approach appears promising for preparing well-formed metal carbonates.

Built-in electric field induced S-scheme g-C_(3)N_(4)homojunction for efficient photocatalytic hydrogen evolution:Interfacial engineering and morphology control

S-scheme possesses superior redox capabilities compared with the II-scheme,providing an effective method to solve the innate defects of g-C_(3)N_(4)(CN).In this study,S-doped g-C_(3)N_(4)/g-C_(3)N_(4)(SCN-tm/CN)S-scheme homojunction was constructed by rationally integrating morphology control with interfacial engineering to enhance the photocatalytic hydrogen evolution performance.In-situ Kelvin probe force microscopy(KPFM)confirms the transport of photo-generated electrons from CN to SCN.Density functional theory(DFT)calculations reveal that the generation of a built-in electric field between SCN and CN enables the carrier separation to be more efficient and effective.Femtosecond transient absorption spectrum(fs-TAS)indicates prolonged lifetimes of SCN-tm/CN_(3)(τ1:9.7,τ2:110,andτ3:1343.5 ps)in comparison to those of CN(τ1:4.86,τ2:55.2,andτ3:927 ps),signifying that the construction of homojunction promotes the separation and transport of electron hole pairs,thus favoring the photocatalytic process.Under visible light irradiation,the optimized SCN-tm/CN_(3)exhibits excellent photocatalytic activity with the hydrogen evolution rate of 5407.3μmol·g^(−1)·h^(−1),which is 20.4 times higher than that of CN(265.7μmol·g^(−1)·h^(−1)).Moreover,the homojunction also displays an apparent quantum efficiency of 26.8%at 435 nm as well as ultra-long and ultra-stable cycle ability.This work offers a new strategy to construct highly efficient photocatalysts based on the metal-free conjugated polymeric CN for realizing solar energy conversion.

Research progress of Ag_3PO_4-based photocatalyst: Fundamentals and performance enhancement

Ag3PO4 is found to be a highly efficient photocatalyst and receives great attention. The high activity of the photocatalyst is credited to the intrinsic electronic structure. The morphology control and nano-composite fabrication are used to improve the performance and practicability. This paper reviews the structure, properties and some theoretical aspects of Ag3PO4 single crystal. Also, the major strategies, namely the morphology control and hetero-nanostructure construction, as ways to improve the performance of Ag3PO4-based photocatalysts, are summarized with the aid of some typical instances.

Recent advances on Bi_(2)WO_(6)‐based photocatalysts for environmental and energy applications

Bismuth tungstate(Bi_(2)WO_(6))has become a research hotspot due to its potential in photocatalytic energy conversion and environmental purification.Nevertheless,the limited light absorption and fast recombination of photogenerated carriers hinder the further improvement of the photocatalytic performance of Bi_(2)WO_(6).Herein,we provide a systematic review for the recent advances on Bi_(2)WO_(6)‐based photocatalysts.It starts with the crystal structure,optical properties and photocatalytic fundamentals of Bi_(2)WO_(6).Then,we focus on the modification strategies of Bi_(2)WO_(6)based on morphology control,atomic modulation and composite fabrication for diverse photocatalytic applications,such as organic synthesis,water splitting,CO2 reduction,water treatment,air purification,bacterial inactivation,etc.Finally,some current challenges and future development prospects are proposed.We expect that this review can provide a useful reference and guidance for the development of efficient Bi_(2)WO_(6)photocatalysts.

Synthesization and crystallization mechanism of nano-scale γ-AlOOH with various morphologies

Nano-scale γ-AIOOH with various morphologies, such as whisker, bar, ball, and sheet, was synthesized successfully and control- lably through a facile hydrothermal method just by adjusting the pH value of the solvent. Based on the analysis of the experimental data, the growth mechanism of nano-scale γ-AlOOH in the hydrothermal process was established. It is proposed that the growth unit and the growth direction are determined by the pH value of the solution and the growth unit, respectively. One-dimensional γ-AlOOH, such as whisker and bar, is formed in lower pH ranges, while two-dimensional γ-AlOOH sueli as sheet is formed only in high pH environment following the plane expansion crystallization mechanism.

Controlled Synthesis and Application of α-Al_2O_3 for Lu_3Al_5O_(12): Ce^(3+) Green Spherical Phosphors

Al2O3 powders with different morphologies,namely fibrous,sheet-like,and spherical,were prepared by the hydrothermal-thermolysis method.Subsequently,polycrystalline,transparent cerium doped lutetium aluminum garnet（Lu3Al5O（12）：Ce^3＋）green phosphors were synthesized by high temperature solidstate method using commercial lutetium（III）oxide,cerium（III）oxide,and as-prepared Al2O3 powders with different morphologies.The phases,morphologies,and photoluminescent properties of the prepared phosphors were investigated by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and photoluminescence spectroscopy（PL）.Moreover,the influences of the morphologies ofα-Al2O3 on the types of crystal structure,morphologies,and photoluminescent properties of LuAG：Ce^3＋green phosphors were investigated.The results indicated that the morphologies and particle sizes of theα-Al2O3 powders could be controlled by the additives and parameters.Notably,the sphericalα-Al2O3 powders with good dispersibility were found to be the excellent base materials of LuAG：Ce^3＋green phosphors for white light emitting diodes.

Photovoltaic-powered supercapacitors for driving overall water splitting:A dual-modulated 3D architecture

Due to the growing demand for clean and renewable hydrogen fuel,there has been a surge of interest in electrocatalytic water-splitting devices driven by renewable energy sources.However,the feasibility of self-driven water splitting is limited by inefficient connections between functional modules,lack of highly active and stable electrocatalysts,and intermittent and unpredictable renewable energy supply.Herein,we construct a dualmodulated three-dimensional(3D)NiCo_(2)O_(4)@NiCo_(2)S_(4)(denoted as NCONCS)heterostructure deposited on nickel foam as a multifunctional electrode for electrocatalytic water splitting driven by photovoltaic-powered supercapacitors.Due to a stable 3D architecture configuration,abundant active sites,efficient charge transfer,and tuned interface properties,the NCONCS delivers a high specific capacity and rate performance for supercapacitors.A twoelectrode electrolyzer assembled with the NCONCS as both the anode and the cathode only requires a low cell voltage of 1.47 V to achieve a current density of 10 mA cm^(−2) in alkaline electrolyte,which outperforms the state-of-the-art bifunctional electrocatalysts.Theoretical calculations suggest that the generated heterointerfaces in NCONCS improve the surface binding capability of reaction intermediates while regulating the local electronic structures,which thus accelerates the reaction kinetics of water electrolysis.As a proof of concept,an integrated configuration comprising a two-electrode electrolyzer driven by two series-connected supercapacitors charged by a solar cell delivers a high product yield with superior durability.

Realization of high performance for PM6:Y6 based organic photovoltaic cells

With advances in material science and a more in-depth understanding of device engineering,the power conversion efficiency(PCE)of solution-processed organic photovoltaic(OPV)cells have significantly boosted in the past few years.In 2019,a high PCE of 15.7%was achieved in the OPV cells adopting a wide bandgap polymer PM6 and a new emerging non-fullerene acceptor Y6.Such outstanding performance has attracted lots of research attention,driving considerable efforts to improve or take advantage of the high-performance PM6:Y6-based system.In this review,we first concentrate on the structural characteristics of PM6 and Y6 with the focus on understanding why their combination for OPV application can obtain such high efficiency.We also update the recent progress in highly efficient PM6:Y6-based OPV cells via various optimizing strategies.Then we summarize the other applications of the PM6:Y6-based system in semi-transparent,flexible or lay e-by-layer devices.The prospects for future OPV studies will be suggested in the end.