Dimethylamine oxalate manipulating CsPbI_(3) perovskite film crystallization process for high efficiency carbon electrode based perovskite solar cells

Crystallization process determines the quality of perovskite films and the performances of resultant perovskite solar cells(PSCs).Dimethylamine oxalate has been proven as a multifunctional modulator,and is explored as an efficient additive in manipulating the crystallization process of CsPbI_(3) perovskite films.On one hand,oxalate serves as the precipitator that facilitates the nucleation process of intermediate.The larger size of intermediate is conductive to the larger size and smaller grain boundaries of resultant perovskite.On the other hand,in subsequent annealing process,the phase conversion and growth process of transient perovskite can be decelerated due to the strong interactions of oxalate with both dimethylamine cation(DMA^(+))and Pb^(2+).Due to the optimized crystallization kinetics,the morphology and quality of CsPbI_(3) perovskite films are comprehensively improved with lower defect concentrations,and charge recombination loss is effectively suppressed.Benefiting from the optimized crystal quality of perovskite films,the carbon electrode-based CsPbI_(3) PSCs exhibit a champion efficiency of 18.48%.This represents one of the highest levels among all hole transport layer-free inorganic perovskite solar cells.

Impact of typical environments in China’s western mountainous areas on the durability of railway concrete:a review

Purpose–This study aims to analyze the impact mechanism of typical environments in China’s western mountainous areas on the durability of railway concrete and propose measures to improve durability.Design/methodology/approach–With the continuous promotion of infrastructure construction,the focus of China’s railway construction has gradually shifted to the western region.The four typical environments of large temperature differences,strong winds and dryness,high cold and low air pressure unique to the western mountainous areas of China have adverse effects on the durability of typical railway structure concrete(bridges,ballastless tracks and tunnels).This study identified the characteristics of four typical environments in the western mountainous areas of China through on-site research.The impact mechanism of the four typical environments on the durability of concrete in different structural parts of railways has been explored through theoretical analysis and experimental research;Finally,a strategy for improving the durability of railway concrete suitable for the western mountainous areas of China was proposed.Findings–The daily temperature difference in the western mountainous areas of China is more than twice that of the plain region,which will lead to significant temperature deformation and stress in the multi-layered structure of railway ballastless tracks.It will result in cracking.The wind speed in the western plateau region is about 2.5 to 3 times that of the plain region,and the average annual rainfall is only 1/5 of that in the plain region.The drying effect on the surface of casting concrete will significantly accelerate its cracking process,leading to serious durability problems.The environmental temperature in the western mountainous areas of China is generally low,and there are more freeze-thaw cycles,which will increase the risk of freeze-thaw damage to railway concrete.The environmental air pressure in the western plateau region is only 60%of that in the plain region.The moisture inside the concrete is more likely to diffuse into the surrounding environment under the pressure difference,resulting in greater water loss and shrinkage deformation of the concrete in the plateau region.The above four issues will collectively lead to the rapid deterioration of concrete durability in the western plateau region.The corresponding durability improvement suggestions from theoretical research,new technology development and standard system was proposed in this paper.Originality/value–The research can provide the mechanism of durability degradation of railway concrete in the western mountainous areas of China and corresponding improvement strategies.

FeCo alloy@N-doped graphitized carbon as an efficient cocatalyst for enhanced photocatalytic H2 evolution by inducing accelerated charge transfer

Cocatalysts play important roles in improving the activity and stability of most photocatalysts.It is of great significance to develop economical,efficient and stable cocatalysts.Herein,using Na2CoFe(CN)6 complex as precursor,a novel noble-metal-free FeCo@NGC cocatalyst(nano-FeCo alloy@N-doped graphitized carbon) is fabricated by a simple pyrolysis method.Coupling with g-C3 N4, the optimal FeCo@NGC/g-C3N4 receives a boosted visible light driven photocatalytic H2 evolution rate of 42.2 μmol h-1, which is even higher than that of 1.0 wt% Pt modified g-C3N4 photocatalyst.Based on the results of density functional theory(DFT) calculations and practical experiment measurements,such outstanding photocatalytic performance of FeCo@NGC/g-C3N4 is mainly attributed to two aspects.One is the accelerated charge transfer behavior,induced by a photogene rated electrons secondary transfer performance on the surface of FeCo alloy nanoparticles.The other is related to the adjustment of H adsorption energy(approaching the standard hydrogen electrode potential) by the presence of external NGC thin layer.Both factors play key roles in the H2 evolution reaction.Such outstanding performance highlights an enormous potential of developing noble-metal-free bimetallic nano-alloy as inexpensive and efficient cocatalysts for solar applications.

Hierarchically porous, ultrathin N–doped carbon nanosheets embedded with highly dispersed cobalt nanoparticles as efficient sulfur host for stable lithium–sulfur batteries

The sluggish redox kinetics and shuttle effect of soluble polysulfides intermediate primarily restrict the electrochemical performance of lithium–sulfur(Li–S) batteries. To address this issue, rational design of high–efficiency sulfur host is increasingly demanded to accelerate the polysulfides conversion during charge/discharge process. Herein, we propose a macro–mesoporous sulfur host(Co@NC), which comprises highly dispersed cobalt nanoparticles embedding in N–doped ultrathin carbon nanosheets. Co@NC is simply synthesized via a carbon nitride–derived pyrolysis approach. Owing to the highly conductive graphene–like matrix and well defined porous structure, the designed multifunctional Co@NC host enables rapid electron/ion transport, electrolyte penetration and effective sulfur trapping. More significantly,N heteroatoms and homogeneous Co nanocatalysts in the graphitic carbon nanosheets could serve as chemisorption sites as well as electrocatalytic centers for sulfur species. These Co–N active sites can synergistically facilitate the redox conversion kinetics and mitigate the shuttling of polysulfides, thus leading to improved electrochemical cycling performance of Li–S batteries. As a consequence, the S/Co@NC cathode demonstrates high initial specific capacity(1505 mA h g-1 at 0.1 C) and excellent cycling stability at 1 C over 300 cycles, giving rise to a capacity retention of 91.7% and an average capacity decline of 0.03%cycle-1.

Modification of compact TiO_(2) layer by TiCl_(4)-TiCl_(3) mixture treatment and construction of high-efficiency carbon-based CsPbI_(2)Br perovskite solar cells

In the construction of high performance planar perovskite solar cells(PSCs),the modification of compact TiO_(2) layer and engineering of perovskite/TiO_(2) interfaces are essential for efficient electron transfer and retarded charge recombination loss.In this work,a facile and effective strategy is developed to modify the surface of compact TiO_(2) layer by TiCl_(4)-TiCl_(3) mixture treatment.Compared with conventional sole TiCl_(4),the TiCl_(4)-TiCl_(3) treatment takes the advantage of accelerated and controlled hydrolysis of TiCl_(3),therefore TiO_(2) with dominating anatase phase and moderate roughness is obtained to facilitate the growth of CsPbI_(2) Br perovskite layer with high quality.Furthermore,the oxidation-driven hydrolysis of TiCl_(3) component results in surface Cl doping that facilitates interfacial electron transfer with retarded recombination loss.The average power conversion efficiency(PCE) of carbon-based CsPbI_(2) Br planar PSCs based on TiCl_(4)-TiCl_(3) treatment increases to 14.18% from the intial 13.04% based on conventional sole TiCl_(4) treatment.The champion PSC exhibits a PCE of 14.46%(V_(oc)=1.28 V,J_(sc)=14.21 mA/cm^(2),and FF=0.794),which is one of the highest PCEs for carbon-based CsPbI_(2) Br PSCs.

Recent Development of Quantum Dot Deposition in Quantum Dot-Sensitized Solar Cells

As new-generation solar cells,quantum dot-sensitized solar cells(QDSCs)have the outstanding advantages of low cost and high theoretical efficiency;thus,such cells receive extensive research attention.Their power conversion efficiency(PCE)has increased from 5%to over 15%in the past decade.However,compared with the theoretical efficiency(44%),the PCE of QDSCs still needs further improvement.The low loading amount of quantum dots(QDs)is a key factor limiting the improvement of cell efficiency.The loading amount of QDs on the surface of the substrate film is important for the performance of QDSCs,which directly affects the light-harvesting ability of the device and interfacial charge recombination.The optimization of QD deposition and the improvement of the loading amount are important driving forces for the rapid development of QDSCs in recent years and a key breakthrough in future development.In this paper,the research progress of QD deposition on the surface of substrate films in QDSCs was reviewed.In addition,the main deposition methods and their advantages and disadvantages were discussed,and future research on the further increase in loading amount was proposed.

Graphene quantum dots assisted photovoltage and efficiency enhancement in CdSe quantum dot sensitized solar cells

CdSe quantum dot sensitized solar cells （QDSCs） modified with graphene quantum dots （GQDs） have been successfully achieved in this work for the first time. Satisfactorily, the optimized photovoltage （Voc） of the modified QDSCs was approximately 0.04 V higher than that of plain CdSe QDSCs, consequently improving the photovoltaic performance of the resulting QDSCs. Served as a novel coating on the CdSe QD sensitized photoanode, GQDs played a vital role in improving Voc due to the suppressed charge recombination which has been confirmed by electron impedance spectroscopy as well as transient photovoltage decay measure- ments. Moreover, different adsorption sequences, concentration and deposition time of GQDs have also been systematically investigated to boost the power conversion efficiency （PCE） of CdSe QDSCs. After the coating of CdSe with GQDs, the resulting champion CdSe QDSCs exhibited an improved PCE of 6.59% under AM 1.5G full one sun illumination.

Selenium cooperated polysulfide electrolyte for efficiency enhancement of quantum dot-sensitized solar cells

The modification of polysulfide electrolyte with additives has been demonstrated as an effective way to improve the photovoltaic performance of quantum dot-sensitized solar cells(QDSCs). Most of these additives can inhibit the charge recombination processes at photoanode/electrolyte interface and favor the improvement of V oc of cell devices. Herein, we showed that the incorporation of elemental selenium(Se) in polysulfide electrolyte to form polyselenosulfide species can notably improve the performance of QDSCs. Unlike previous reports, we present here an integrated investigation of the effects of polyselenosulfide species in polysulfide electrolyte on the photovoltaic performance of QDSCs from both of the photoanode and counter electrode(CE) aspects. Electrochemical impedance spectroscopy(IS) and opencircuit voltage-decay(OCVD) measurements demonstrated that the introduction of Se into polysulfide electrolyte can not only retard charge recombination at photoanode/electrolyte interface, but also reduce the charge transfer resistance at CE/electrolyte interface, resulting in the improvement of J sc and FF values. Consequently, the average efficiency of Zn-Cu-In-Se QDSCs was improved from 9.26% to 9.78% under AM 1.5 G full one sun illumination.

Bi_(2)S_(3) Nanostructures: A New Photocatalyst

Uniform colloidal Bi_(2)S_(3) nanodots and nanorods with different sizes have been prepared in a controllable manner via a hot injection method. X-ray diffraction (XRD) results show that the resulting nanocrystals have an orthorhombic structure. Both the diameter and length of the nanorods increase with increasing concentration of the precursors. All of the prepared Bi_(2)S_(3) nanostructures show high efficiency in the photodegradation of rhodamine B, especially in the case of small sized nanodots-which is possibly due to their high surface area. The dynamics of the photocatalysis is also discussed.

Growth of Anisotropic Platinum Nanostructures Catalyzed by Gold Seed Nanoparticles

This paper reports an effective method for the synthesis of platinum nanostructures with anisotropic morphologies by decomposition of platinum dichloride in oleylamine at intermediate temperatures catalyzed by gold seed nanoparticles.A small quantity of spherical gold nanoparticles formed in situ was used to trigger the nucleation and anisotropic growth of the Pt nanocrystals.By varying the amount of gold seed nanoparticles,porous fl ower-like,irregular polyhedron-shaped,multi-branched rod shaped,and caterpillar-like Pt nanostructures were produced in high yields at 190240°C in reaction times of a few minutes.Control of morphology under different conditions has been systematically studied and a kinetically controlled induced growth mechanism has been proposed.

Self-supported metal sulphide nanocrystals-assembled nanosheets on carbon paper as efficient counter electrodes for quantum-dotsensitized solar cells

Developing efficient counter electrodes(CEs)and quantum dots made of earth-abundant and non-toxic elements is essential but still challenging for quantum dot-sensitized solar cells(QDSSCs).Here,we report a facile strategy to prepare self-supported and robust CoS_2and NiS nanocrystals-assembled nanosheets directly grown on carbon paper(MS_xNS@CP)as efficient counter electrodes for QDSSCs.Such CEs integrate the merits of fast electron transfer from interconnected conductive scaffold,efficient mass transfer from hierarchically vertical nanosheet on 3D open substrate,as well as abundant highly active catalytic sites from metal sulphide nanocrystal units.As a result,QDDSCs based on such CoS_2NS@CP and NiS NS@CP CEs achieve a PCE of8.88%and 7.53%,respectively.The detailed analyses suggest that CoS_2NS@CP has the highest catalytic activity and shows the lowest charger transfer resistance,leading to the highest PCE.These findings may inspire the design and exploration of other self-supported efficient CEs by integrating highly active catalysts onto 3D conductive networks for efficient QDSSCs.