Bifunctional passivation by lewis-base molecules for efficient printable mesoscopic perovskite solar cells

Printable mesoscopic perovskite solar cells(PM-PSCs)possess notable merits in terms of cost-effectiveness,easy manufacturing,and large scale applications.Nevertheless,the absence of a hole transport layer contributes to the exacerbation of carrier recombination,and the defects between the perovskite and electron transport layer(ETL)interfaces significantly decrease the efficiency of the devices.In this study,a bifunctional surface passivation approach is proposed by applying a thioacetamide(TAA)surfactant on the mesoporous TiO_(2)interface.The results demonstrate that TAA molecules could interact with TiO_(2),thereby diminishing the oxygen vacancy defects.Additionally,the amino group and sulfur atoms in TAA molecules act as Lewis base to effectively passivate the uncoordinated Pb^(2+)in perovskite and improve the morphology of perovskite,and decrease the trap-state density of perovskite.The TAA passivation mechanism improves the alignment of energy levels between TiO_(2)and perovskite,facilitating electron transport and reducing carrier recombination.Consequently,the TAA-passivated device achieved a champion power conversion efficiency(PCE)of 17.86%with a high fill factor(FF)of 79.16%and an open-circuit voltage(V_(OC))of 0.971 V.This investigation presents a feasible strategy for interfacial passivation of the ETL to further improve the efficiency of PM-PSCs.

From concept to reality-A review to the primary test stand and its preliminary application in high energy density physics

Pulsed power technology,whereas the electrical energy stored in a relative long period is released in much shorter timescale,is an efficient method to create high energy density physics(HEDP)conditions in laboratory.Around the beginning of this century,China Academy of Engineering Physics(CAEP)began to build some experimental facilities for HEDP investigations,among which the Primary Test Stand(PTS),a multi-module pulsed power facility with a nominal current of 10 MA and a current rising time~90 ns,is an important achievement on the roadmap of the electro-magnetically driven inertial confinement fusion(ICF)researches.PTS is the first pulsed power facility beyond 10 TW in China.Therefore,all the technologies have to be demonstrated,and all the engineering issues have to be overcome.In this article,the research outline,key technologies and the preliminary HEDP experiments are reviewed.Prospects on HEDP research on PTS and pulsed power development for the next step are also discussed.

Recent Advances in Wide-Bandgap Organic-Inorganic Halide Perovskite Solar Cells and Tandem Application

Perovskite-based tandem solar cells have attracted increasing interest because of its great potential to surpass the Shockley-Queisser limit set for single-junction solar cells.In the tandem architectures,the wide-bandgap(WBG)perovskites act as the front absorber to offer higher open-circuit voltage(VOC)for reduced thermalization losses.Taking advantage of tunable bandgap of the perovskite materials,the WBG perovskites can be easily obtained by substituting halide iodine with bromine,and substituting organic ions FA and MA with Cs.To date,the most concerned issues for the WBG perovskite solar cells(PSCs)are huge VOC deficit and severe photo-induced phase separation.Reducing VOC loss and improving photostability of the WBG PSCs are crucial for further efficiency breakthrough.Recently,scientists have made great efforts to overcome these key issues with tremendous progresses.In this review,we first summarize the recent progress of WBG perovskites from the aspects of compositions,additives,charge transport layers,interfaces and preparation methods.The key factors affecting efficiency and stability are then carefully discussed,which would provide decent guidance to develop highly efficient and stable WBG PSCs for tandem application.

Improved perovskite solar cell efficiency by tuning the colloidal size and free ion concentration in precursor solution using formic acid additive

Improving the quality of the perovskite active layer is crucial to obtaining high performance perovskite solar cells(PSCs). In this work, by introducing formic acid into the formamidinium lead iodide(FAPbI3)precursor solution, we managed to achieve reduced colloidal size in the solution, leading to more uniform deposition of FAPbI3 film with lower trap state density and higher carrier mobility. The solar cells based on the FAPbI3 absorber layer modified with formic acid show significantly better photovoltaic performance than that on the reference FAPbI3 film without formic acid. The device performance shows a close correlation with the colloidal size. Within the range studied from 6.7 to 1.0 nm, the smaller the colloidal size is, the higher the solar cell efficiency. More specifically, the cell efficiency is improved from17.82% for the control cell without formic acid to 19.81% when 0.764 M formic acid was used. Formic acid has also been added into a CH3NH3PbI3(MAPbI3) precursor solution, which exhibits a similar effect on the resulting MAPb I3 films and solar cells, with efficiency improved from 16.07% to 17.00%.

Post-treatment by an ionic tetrabutylammonium hexafluorophosphate for improved efficiency and stability of perovskite solar cells

Interface engineering is an effective way to improve efficiency and long-term stability of perovskite solar cells(PSCs).Herein,an ionic compound tetrabutylammonium hexafluorophosphate(TP6)is adopted to passivate surface defects of the perovskite film.It is found that TP6 effectively reduced the surface defects,especially at the grain boundaries where the defects are abundant.Meanwhile,the exposed long alkyl chains and fluorine atoms in the TP6 enhanced the moisture stability of the perovskite film due to its strong hydrophobicity.In addition,the driving force of charge carrier separation and transport is increased by enlarged built-in potential.Consequently,the power conversion efficiency(PCE)of PSCs is significantly improved from 20.59% to 22.41%by increased open-circuit voltage(V_(oc))and fill factor(FF).The unencapsulated device with TP6 treatment exhibits better stability than the control device,and the PCE retains-80%of its initial PCE after 30 days under 15%-25%relative humidity in storage,while the PCE of the control device declines by more than 50%.

Green antisolvent additive engineering to improve the performance of perovskite solar cells

High-quality perovskite films with larger grain size and fewer defects is a prerequisite for highperformance perovskite solar cells(PSCs).Antisolvent-assisted crystallization is an effective approach to obtain compact and uniform perovskite films;however,the majority of antisolvents currently applied have strong toxicity,and the control of perovskite crystallization is not easy through single antisolvent.In this work,a green antisolvent of ethyl acetate(EA)with acetylacetone(AA)additive is used to fine-tune perovskite crystallization and passivate defect,which produces uniform and compact CH;NH;PbI;perovskite films having larger grain and fewer grain boundaries and reduced defect density.Meanwhile,the interfacial hydrophobic characteristic of the perovskite films is enhanced.At the optimized concentration of AA in EA,the power conversion efficiency(PCE)of the CH;NH;PbI;PSCs was improved from 19.2%to 21.1%and their stability in air was also enhanced.These results present a green antisolvent additive engineering strategy to enhance the crystallinity,passivate defects,and fabricate efficient and stable PSCs.

A gas-kinetic theory based multidimensional high-order method for the compressible Navier–Stokes solutions

This paper presents a gas-kinetic theory based multidimensional high-order method for the compressible Naiver–Stokes solutions. In our previous study, a spatially and temporally dependent third-order flux scheme with the use of a third-order gas distribution function is employed.However, the third-order flux scheme is quite complicated and less robust than the second-order scheme. In order to reduce its complexity and improve its robustness, the secondorder flux scheme is adopted instead in this paper, while the temporal order of method is maintained by using a two stage temporal discretization. In addition, its CPU cost is relatively lower than the previous scheme. Several test cases in two and three dimensions, containing high Mach number compressible flows and low speed high Reynolds number laminar flows, are presented to demonstrate the method capacity.

Short-term Prediction of Ionospheric TEC Based on ARIMA Model

In order to achieve high short-term prediction accuracy of ionospheric TEC,first,we transform a seasonal time series for ionospheric Total Electron Content (TEC) into a stationary time series by seasonal differences and regular differences with a full consideration of the Multiplicative Seasonal model.Next,we use the Autoregressive Integrated Moving Average (ARIMA) model taken from time series analysis theory for modeling the stationary TEC values to predict the TEC series.Using TEC data from 2008 to 2012 provided by the Center for Orbit Determination in Europe (CODE) as sample data,we analyzed the precision of this method for prediction of ionospheric TEC values which vary from high to low latitudes during both quiet and active ionospheric periods.The effect of the TEC sample’s length on the predicted accuracy is analyzed,too.Results from numerical experiments show that during the ionospheric quiet period the average relative prediction accuracy for a six day time span reaches up to 83.3% with average prediction residual errors of about 0.18±1.9 TECu.During ionospheric active periods it changes to 86.6% with an average prediction residual error of about 0.69±2.6 TECu.For the quiet periods,above 90% of predicted residual is less than ±3 TECu while during active periods,it is only about 81%.The two periods show that that the higher the latitude,the higher the absolute precision,and the lower the predicted relative accuracy.In addition,the results show that prediction accuracy will improve with an increase of the TEC sample sequences length,but it will gradually reduce if the length exceeds the optimal length,about 30 days.On the other hand,with the same TEC sample,as the predicted days increase,the predictive accuracy decreases.Athough the predictive accuracy is not apparent at the beginning,it will be significantly reduced after 30 days.

Cures for expansion shock and shock instability of Roe scheme based on momentum interpolation mechanism

The common defects of the Roe scheme are the non-physical expansion shock and shock instability. By removing the momentum interpolation mechanism(MIM), an improved method with several advantages has been presented to suppress the shock instability. However, it cannot prevent the expansion shock and is incompatible with the traditional curing method for expansion shock. To solve the problem, the traditional curing mechanism is analyzed. Effectiveness of the traditional curing method is discussed,and several defects are identified, one of which leads to incompatibility between curing shock instability and expansion shock. Consequently, an improved Roe scheme is proposed, which is with low computational costs, concise, easy to implement, and robust.More importantly, the proposed scheme can simultaneously solve the problem of shock instability and expansion shock without additional costs.

On the Poverty in the Rocky Desertification Areas of Southwest China Based on AHP: A Case Study of Liupanshui City in Guizhou Province

Karst rocky desertification mountain areas are regarded as main positions to wipe out poverty for their large poverty population,wide poverty area,high rate of poverty,etc. This paper takes Liupanshui city as an example where the situation of rocky desertification is very serious. We build the indicator system of poverty alleviation and development by analyzing their poverty and using the AHP method and also find the limiting factors which restrict the development of this area then put forward the recommendations to alleviate poverty.

Progress of Geodesy Related Ionosphere from Chinese Scientists in the Period of 2019—2023

The ionosphere is the ionized part of the upper atmosphere of the Earth,which plays an important role in atmospheric electricity and forms the inner edge of the magnetosphere.It influences radio propagation significantly,such as the Global Navigation Satellite System(GNSS).Meanwhile,the GNSS is also an essential technique for sensing the variation of ionosphere.During the years of 2019—2023,a large number of Chinese geodesy scientists devoted much efforts to the geodesy related ionosphere.Due to the very limited length,the achievements are carried out from the following six aspects,including:①The ionospheric correction models for BDS and BDSBAS;②Real-time global ionospheric monitoring and modeling;③The ionospheric 2D and 3D modeling based on GNSS and LEO satellites;④The ionospheric prediction based on artificial intelligence;⑤The monitoring and mitigation of ionospheric disturbances for GNSS users;⑥The ionospheric related data products and classical applications.

An improved deviation model for transonic stages in axial compressors

Deviation model is an important model for through-flow analysis in axial compressors.Theoretical analysis in classical deviation models is developed under the assumption of onedimensional flow,which is controlled by the continuity equation.To consider three-dimensional characteristics in transonic flow,this study proposes an improved theoretical analysis method combining force analysis of the blade-to-blade flow with conventional analysis of the continuity equation.Influences of shock structures on transverse force,streamwise velocity and streamline curvature in the blade-to-blade flow are analyzed,and support the analytical modelling of density flow ratio between inlet and outlet conditions.Thus,a novel deviation model for transonic stages in axial compressors is proposed in this paper.The empirical coefficients are corrected based on the experimental data of a linear cascade,and the prediction accuracy is validated with the experimental data of a three-stage transonic compressor.The novel model provides accurate predictions for meridional flow fields at the design point and performance curves at design speed,and shows obvious improvements on classical models by Carter and C¸etin.

Novel synthesis of N-doped graphene as an efficient electrocatalyst towards oxygen reduction

Nitrogen-doped graphene （NG） was successfully synthesized by a novel, facile, and scalable bottom-up method. The annealed NG （NG-A） possessed high specific surface area and a hierarchical porous texture, and exhibited remarkably improved electrocatalytic activity in the oxygen reduction reaction in both alkaline and acidic media. Ab initio molecular dynamic simulations indicated that rapid H transfer and the thermodynamic stability of six-membered N structures promoted the transformation of N-containing species from pyrrolic to pyridinic at 600 ℃ In O2-staturated 0.1 M KOH solution, the half-wave potential （El/2） of NG-A was only 62 mV lower than that of a commercial Pt/C catalyst, and the limiting current density of NG-A was 0.5 mA.cm-2 larger than that of Pt/C. Koutecky-Levich （K-L） plots and rotating ring-disk electrode measurement indicated a four-electron- transfer pathway in NG-A, which could be ascribed to its high content of pyridinic N.

Improvement of part-load performance of gas turbine by adjusting compressor inlet air temperature and IGV opening

A novel adjusting method for improving gas turbine(GT)efficiency and surge margin(SM)under partload conditions is proposed.This method adopts the inlet air heating technology,which uses the waste heat of lowgrade heat source and the inlet guide vane(IGV)opening adjustment.Moreover,the regulation rules of the compressor inlet air temperature and the IGV opening are studied comprehensively to optimize GT performance.A model and calculation method for an equilibrium running line is adopted based on the characteristic curves of the compressor and turbine.The equilibrium running lines calculated through the calculation method involve three part-load conditions and three IGVopenings with different inlet air temperatures.The results show that there is an optimal matching relationship between IGV opening and inlet air temperature.For the best GT performance of a given load,the IGV could be adjusted according to inlet air temperature.In addition,inlet air heating has a considerable potential for the improvement of part-load performance of GT due to the increase in compressor efficiency,combustion efficiency,and turbine efficiency as well as turbine inlet temperature,when inlet air temperature is lower than the optimal value with different IGV openings.Further,when the IGV is in a full opening state and an optimal inlet air temperature is achieved by using the inlet air heating technology,GT efficiency and SM can be obviously higher than other IGVopenings.The IGV can be left unadjusted,even when the load is as low as 50%.These findings indicate that inlet air heating has a great potential to replace the IGV to regulate load because GT efficiency and SM can be remarkably improved,which is different from the traditional viewpoints.

120 mm Single-crystalline perovskite and wafers： towards viable applications

As the large single-crystalline silicon wafers have revolutionized many industries including electronics and solar cells, it is envisioned that the availability of large single-crystalline perovskite crystals and wafers will revolutionize its broad applications in photovoltaics, optoelectronics, lasers, photodetectors, light emitting diodes(LEDs), etc. Here we report a method to grow large single-crystalline perovskites including single-halide crystals: CH3NH3PbX3(X=I, Br, Cl), and dual-halide ones:CH3NH3Pb(ClxBr1.x)3 and CH3NH3Pb(BrxI1.x)3, with the largest crystal being 120 mm in length. Meanwhile, we have advanced a process to slice the large perovskite crystals into thin wafers. It is found that the wafers exhibit remarkable features:(1)its trap-state density is a million times smaller than that in the microcrystalline perovskite thin films(MPTF);(2) its carrier mobility is 410 times higher than its most popular organic counterpart P3HT;(3) its optical absorption is expanded to as high as910 nm comparing to 797 nm for the MPTF;(4) while MPTF decomposes at 150 °C, the wafer is stable at high temperature up to270 °C;(5) when exposed to high humidity(75% RH), MPTF decomposes in 5 h while the wafer shows no change for overnight;(6) its photocurrent response is 250 times higher than its MPTF counterpart. A few electronic devices have been fabricated using the crystalline wafers. Among them, the Hall test gives low carrier concentration with high mobility. The trap-state density is measured much lower than common semiconductors. Moreover, the large SC-wafer is found particularly useful for mass production of integrated circuits. By adjusting the halide composition, both the optical absorption and the light emission can be fine-tuned across the entire visible spectrum from 400 nm to 800 nm. It is envisioned that a range of visible lasers and LEDs may be developed using the dual-halide perovskites. With fewer trap states, high mobility, broader absorption, and humidity resistance, it is expected that solar cells with high stable efficiency maybe attainable using the crystalline wafers.

Chlorine-modified SnO2 electron transport layer for high-efficiency perovskite solar cells

A high-quality electron transport layer(ETL)is a critical component for the realization of high-efficiency perovskite solar cells.We developed a controllable direct-contact reaction process to prepare a chlorinated SnO2(SnO2-Cl)ETL.It is unique in that(a)102-dichlorobenzene is used to provide more reactive Cl radicals for more in-depth passivation;(b)it does not introduce any impurities other than chlorine.It is found that the chlorine modification significantly improves the electron extraction.Consequently,its associated solar cell efficiency is increased from 17.01%to 17.81%comparing to the pristine SnO2 ETL without the modification.The hysteresis index is significantly reduced to 0.017 for the SnO2-Cl ETL.

Effect of inverted T arrangement on AC pollution flashover characteristics of insulator strings

The arrangement of insulator strings has an effect on its pollution flashover characteristics.A new arrangement of insulator strings,inverted T-type arrangement,is proposed in this study.The electric field distribution is simulated and the pollution flashover characteristics are tested in an artificial climate chamber.The test results indicate that the inverted T-type arrangement can greatly improve the flashover voltage of polluted insulator strings,the‘7+2’inverted T-type arrangement can increase the flashover voltage of each insulator by 8.5%on average,and the‘3+3’inverted T-type arrangement can increase the flashover voltage of each insulator by 13.4%.The discharge process is different from that of the normal suspension string when the insulator string is inverted T-shaped,i.e.a local arc is produced at the low voltage end of the insulator string and develops downward along the suspension part.While as for the horizontal tension string parts,it is difficult to generate arc during discharge development.

钙钛矿叠层太阳电池中电荷传输材料的研究进展

开发钙钛矿叠层太阳电池是一种可以突破单结太阳电池Shockley-Queisser极限的光伏技术.令人鼓舞的是,所有钙钛矿叠层器件,包括钙钛矿/硅、钙钛矿/钙钛矿、钙钛矿/铜铟镓硒和钙钛矿/有机叠层电池,都表现出比相应单结太阳电池更高的效率,显示出巨大的进一步突破的潜力.在叠层器件中,电荷传输材料是钙钛矿子电池的重要组成部分,它直接决定了器件的电荷传输和能量损失.一般来说,高导电性和透光性、良好的能级和化学稳定性是电荷传输材料叠层应用的关键.迄今为止,导电金属氧化物、有机分子、聚合物、富勒烯、自组装材料等各种电荷传输材料已被广泛应用于高效叠层电池.在本文中,我们首先总结了不同类型钙钛矿叠层电池的电荷传输材料的最新进展,详细讨论了材料的电学和光学性质及其对器件性能的影响.在此基础上,我们提出了叠层电池中电荷传输材料进一步发展所面临的挑战和展望.本综述将为不同钙钛矿叠层太阳电池的器件设计提供有效指导.

Investigating GNSS PPP-RTK with external ionospheric constraints

Real-Time Kinematic Precise Point Positioning(PPP–RTK)is inextricably linked to external ionospheric information.The PPP-RTK performances vary much with the accuracy of ionospheric information,which is derived from diferent network scales,given diferent prior variances,and obtained under diferent disturbed ionospheric conditions.This study investigates the relationships between the PPP–RTK performances,in terms of precision and convergence time,and the accuracy of external ionospheric information.The statistical results show that The Time to First Fix(TTFF)for the PPP-RTK constrained by Global Ionosphere Map(PPP-RTK-GIM)is about 8–10 min,improved by 20%–50%as compared with that for PPP Ambiguity Resolution(PPP-AR)whose TTFF is about 13–16 min.Additionally,the TTFF of PPP-RTK is 4.4 min,5.2 min,and 6.8 min,respectively,when constrained by the external ionospheric information derived from diferent network scales,e.g.small-,medium-,and large-scale networks,respectively.To analyze the infuences of the optimal prior variances of external ionospheric delay on the PPP–RTK results,the errors of 0.5 Total Electron Content Unit(TECU),1 TECU,3 TECU,and 5 TECU are added to the initial ionospheric delays,respectively.The corresponding convergence time of PPP–RTK is less than 1 min,about 3,5,and 6 min,respectively.After adding the errors,the ionospheric information with a small variance leads to a long convergence time and that with a larger variance leads to the same convergence time as that of PPP-AR.Only when an optimal prior variance is determined for the ionospheric delay in PPP-RTK model,the convergence time for PPP-RTK can be shorten greatly.The impact of Travelling Ionospheric Disturbance(TID)on the PPP-RTK performances is further studied with simulation.It is found that the TIDs increase the errors of ionospheric corrections,thus afecting the convergence time,positioning accuracy,and reliability of PPP-RTK.

Highly stable and efficient perovskite solar cells produced via high-boiling point solvents and additive engineering synergistically

The active absorber layer plays a crucial role in a perovskite solar cell.Herein,we used high boiling pointγ-butyrolactone(GBL)as the main solvent,Pb(SCN)2 and dimethyl sulfoxide(DMSO)as an effective additive in the FA0.83MA0.17Cs0.05PbI(3-x)Brx solution to improve the quality of perovskite films.The GBL will delay the crystallization speed of the perovskite,and lead to the grain growth assisted by thiocyanate.The synergistic effect of the solvent engineering and additive engineering is beneficial to the slow growth of the grain size.It is found that the addition of Pb(SCN)2 increases Gibbs free energy barrier for the nucleation,leading to the formation of fewer nuclei,which results in a high quality of perovskite absorbers with larger grains and smoother surfaces.The synergistic effect of solvents and Pb(SCN)2 on the morphology and photovoltaic performances is investigated.Compared to devices without the additive,the efficiency of devices with 5%Pb(SCN)2-doped FA0.83MA0.17Cs0.05PbI(3-x)Brx is raised to 19.01%from 15.21%.We believe this breakthrough regarding high efficiency perovskite solar cells will help for their transitions.