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Shallow soil refers to the soil layer within the 50 cm depth. Shallow soil temperature (ST) directly or indirectly affects many processes in the soil, such as seed germination, plant growth, and water evaporation. Therefore, the study of shallow ST is of great significance in understanding the surface energy, water cycle, ecology and climate change. This work collected observational data from 141 meteorological stations on the Qinghai-Tibet Plateau from 1981 to 2020 and ERA5 reanalysis data, used the “Moving Surface Spline Interpolation Algorithm Based on Green’s Function” and “Fuzzy C-means algorithm”, and analyzed the temporal and spatial change characteristics of ST at different levels. The results showed that 1) the temperature increase of 0–20 cm (the surface layer of the shallow soil) was roughly the same. The average annual ST was 9.15–9.57°, and the interdecadal variabilities were 0.49–0.53 K/10a. The average annual ST of 40 cm (the bottom layer) was 8.69°, and the interdecadal variability reached 0.98 K/10a. 2) Considering the 7 regions, the warming trend was obvious, and there were certain regional differences. The average annual ST in different regions ranged from 5.2 (northeastern Plateau) to 17.1 °C (western Sichuan Plateau), with a difference of nearly 12 K. The standard deviation ranged from 0.40 (western Sichuan Plateau) to 0.61 K (Qiangtang Plateau), with a difference of 0.21 K. 3) The errors of the obtained grid data were basically less than 3%, which were much smaller than the errors obtained from the ERA5 reanalysis data. This work is significant for understanding the characteristics of ST evolution and land‒atmosphere interactions on the Qinghai-Tibet Plateau and provides important data support for improving the underlying surface boundary conditions of models.

Gas hydrate is a nonstoichiometric crystalline material. It is attracting more and more attention not only because natural gas hydrate is a potential energy resource, but also because hydrate-based technologies can be potentially applied to the industry of energy and environment such as energy storage, carbon sequestration, etc. The nucleation mechanism of gas hydrate is a key issue in studying reservoir formation of natural gas hydrate and the kinetic properties of gas hydrate as an energy-storage media. Molecular dynamics simulation can provide microscopic insights into molecular-scale understanding of hydrate nucleation. In this review, the advances on the study of heterogeneous hydrate nucleation by molecular dynamics simulation are summarized, with a specific focus on the factors affecting nucleation processes. The interfacial energy barrier for nucleation will be lowered by molecular structure of interfacial water between hydrate and solid substrate. The interface and surface properties of solid substrate, including hydrophilicity and hydrophobicity, surface roughness, layer-accumulated adsorption potential, crystallinity and surface layer-charge are also recognized as being associated with the process of hydrate nucleation by influencing the dynamics of gas and water molecules. In case of hydrate nucleation in confined pore space, confinement effect, pore size and elasticity are identified as the controlling factors.

Quasi-2D perovskites have long been considered to have favorable "energy funnel/cascade" structures and excellent optical properties compared with their 3D counterparts. However, most quasi-2D perovskite light-emitting diodes (PeLEDs) exhibit high external quantum efficiency (EQE) but unsatisfactory operating stability due to Auger recombination induced by high current density. Herein, a synergetic dual-additive strategy is adopted to prepare perovskite films with low defect density and high environmental stability by using 18-crown-6 and poly(ethylene glycol) methyl ether acrylate (MPEG-MAA) as the additives. The dual additives containing COC bonds can not only effectively reduce the perovskite defects but also destroy the self-aggregation of organic ligands, inducing the formation of perovskite nanocrystals with quasi-core/shell structure. After thermal annealing, the MPEG-MAA with its CC bond can be polymerized to obtain a comb-like polymer, further protecting the passivated perovskite nanocrystals against water and oxygen. Finally, state-of-the-art green PeLEDs with a normal EQE of 25.2% and a maximum EQE of 28.1% are achieved, and the operating lifetime (T50 ) of the device in air environment is over ten times increased, providing a novel and effective strategy to make high efficiency and long operating lifetime PeLEDs.

Polythiophenes (PTs) are promising donor materials for the industrialization of polymer solar cells (PSCs) due to the merits of easy synthesis, low cost, and large-scale producibility. The rapid progress of non-fullerene acceptors requires the development of new PTs for use in non-fullerene PSCs. In this work, we present a set of PTs with different degrees of backbone fluorination (P6T-F00, P6T-F50, P6T-F75, and P6T-F100) to investigate the effect of fluorination on the photovoltaic properties of PTs in non-fullerene PSCs. Upon increasing fluorine content, the PTs tend to have higher crystallinity, higher absorption coefficients, and enhanced relative dielectric constants. When blended with a non-fullerene acceptor EH-IDTBR, the blend films show increased photoluminescence quenching efficiency, reduced charge recombination loss, and extended charge carrier lifetime along with increasing fluorine content of PTs. These positive factors collectively result in dramatically improved power conversion efficiency...

Molecular dynamics simulations were performed to study the effects of temperatures, pressures, and methane mole fractions on the generation behaviors, dynamic properties, and interfacial structures of methane gas bubbles. Methane gas bubbling can be promoted by high temperatures and high mole fractions of methane, which come from the generation of larger methane clusters in solution. Bubbles were found to be highly dynamic, with more methane molecules exchanging between bubbles and the surrounding solution at high pressures and in systems with high mole fractions of methane. The interfacial structures between bubbles and the surrounding solution were rough at a molecular level, and the roughness of the outermost methane and water molecules was high at high temperatures, low pressures, and in systems with high methane mole fractions. The dissolution of methane molecules depended on the interactions between the outermost methane and water molecules, which would become stronger with decreasing temperatures, increasing pressures, and decreasing methane mole fractions. The results obtained can help in understanding both the generation behaviors of bubbles when gas hydrates decompose and the re-nucleation behaviors of gas hydrates in the presence of bubbles.

Hypothesis Quartz is one of the most common but important minerals, and its wettability plays a significant role in affecting various natural and industrial processes. Studies have revealed that different crystal faces of quartz are with different wettabilities, but its mechanism is still vague. Experiments and simulations For specifying the mechanism of crystal face dependent wettability, the contact angles of three different liquids on the crystal faces of α-quartz are measured; the time-of-flight secondary ion mass spectrometry (ToF-SIMS) is employed to establish the crystal surface models; molecular dynamics (MD) simulations with the surface models are performed to understand the wetting behavior at molecular scale. Findings Based on the contact angle measurements, the wettabilities of different crystal faces of α-quartz are found different, which can be directly attributed to the concentration of hydroxyl group on crystal faces based on ToF-SIMS results. MD simulations yield consistent results with the contact angle order recognized from experiments, revealing that the surface hydroxyl group controls the wettability of α-quartz crystal faces. It is also recognized that the pristine surface atomic arrangement, especially the surface concentration of unsaturated bond (an intrinsic property of α-quartz), is the intrinsic cause of the difference in the concentration of hydroxyl group of the crystal surface.

This study selected the two adjacent eddy covariance observational towers at the FPV in Yangzhong, Jiangsu Province of China to explore the issue. The results indicated that the percent frequency of east wind lower 4 m·s-1 at 2 m decreased by 25.3% in FPV site compared with the REF site. The FPV array have a heating effect on the ambient. The average air temperature difference in two sites at 2 m and 10 m are 0.3 K and 0.1 K during the heating period. The net radiation increased by 47.8 W·m-2 in two sites. Sensible heat is increased by 7.9 W·m-2 due to the heating effect. Latent heat in the two sites are contrary to the sensible heat (-13.0 W·m-2). The difference of the water storage heat is 32.18 W·m-2, which implies the water absorbs higher heat in the FPV site than the REF site. This work illustrated the importance of observational experiments to animate process-based understanding combined with FPV systems. It further provides the scientific basis to establish the FPV energy balance models based on the observation that may be used to reveal the impact of utility-scale FPV deployment on climatic effects.

We used the data of observational site in photovoltaic power plant (PV site) and reference site in summer 2020 to compare the characteristics of surface energy flux of PV site and Gobi underlying surface. We defined the photovoltaic virtual flux and calculated the proportion of photovoltaic power generation in the net radiation by using daily power generation and generating hours. The results show that the net radiation of PV site was larger than that of reference site throughout the day. Compared with the reference site, the sensible heat flux and latent heat flux of PV site increased by 6% and 53.5%, respectively. Sensible heat flux, soil heat flux, latent heat flux and photovoltaic virtual flux accounted for 43.2%, 14.5%, 8.6% and 6.1% of the net radiation, respectively. The sensible heat accounted for the largest proportion, the energy balance closure increased from 0.6 to 0.67 in the daytime.

A high-performance monolithic perovskite/organic tandem solar cell based on the integration of a large bandgap CsPbI2Br inorganic perovskite front cell with a narrow bandgap PM6:Y6-based or PTB7-Th:O6T-4F-based bulk-heterojunction organic rear cell is demonstrated. Large bandgap inorganic perovskites are well suited candidates for the front cell due to their excellent optoelectronic properties and broad absorption for visible light, they also possess smaller voltage loss (Eloss) and higher external quantum efficiency (EQE) response when compare to their organic counterparts with approximate bandgap. Low bandgap organic solar cells offer potentially better stability and absorption tunability compared with the Sn-based perovskite counterparts, making them be good candidates for the rear cell of the tandem cells. As a result, the best power conversion efficiency (PCE) of the perovskite/organic tandem cell presented in this work reaches over 18%. In addition, based on the photovoltaic performance parameters (EQE, fill factor (FF), Eloss) that have already been achieved in state-of-the-art organic and perovskite solar cells, we further evaluate the potential PCE of the perovskite/organic tandem cells, showing a maximum calculated PCE of over 31% when the bandgaps of the subcells are optimized. This work paves the way for the development of hybrid tandem solar cells with promising performance.

Here we provide a comprehensive review of a newly developed lighting technology based on metal halide perovskites (i.e. perovskite light-emitting diodes) encompassing the research endeavours into materials, photophysics and device engineering. At the outset we survey the basic perovskite structures and their various dimensions (namely three-, two- and zero-dimensional perovskites), and demonstrate how the compositional engineering of these structures affects the perovskite light-emitting properties. Next, we turn to the physics underpinning photo- and electroluminescence in these materials through their connection to the fundamental excited states, energy/charge transport processes and radiative and non-radiative decay mechanisms. In the remainder of the review, we focus on the engineering of perovskite light-emitting diodes, including the history of their development as well as an extensive analysis of contemporary strategies for boosting device performance. Key concepts include balancing the electron/hole injection, suppression of parasitic carrier losses, improvement of the photoluminescence quantum yield and enhancement of the light extraction. Overall, this review reflects the current paradigm for perovskite lighting, and is intended to serve as a foundation to materials and device scientists newly working in this field.

The effects of soil seasonal freezing and thawing process on land surface heat fluxes were analyzed with two years observation data from 2013 to 2014 . The results showed that the sensible heat, latent heat and soil heat flux have no change significantly during the soil freezing stage. The sensible heat flux increased significantly, the latent heat flux decreased significantly, and the corresponding wave ratio increased during the frozen period. The soil moisture and soil heat flux increases rapidly, sensible heat flux and surface long wave radiation decrease rapidly, latent heat flux increases rapidly during the thawing stage. The thawing process of frozen soil has an obvious effect on the heat flux of soil, which increases the heat flux from surface soil to deep soil because of that the heat absorption of ice in thawing process.

Summary Low-band-gap metal halide perovskite semiconductor based on mixed Sn/Pb is a key component to realize high-efficiency tandem perovskite solar cells. However, the mixed perovskites are unstable in air due to the oxidation of Sn2+. To overcome the stability problem, we introduced N-(3-aminopropyl)-2-pyrrolidinone into the CH3NH3Sn0.5Pb0.5IxCl3-x thin film. The carbonyl group on the molecule interacts with Sn2+/Pb2+ by Lewis acid coordination, forming vertically oriented 2D layered perovskite. The 2D phase is seamlessly connected to the bulk perovskite crystal, with a lattice coherently extending across the two phases. Based on this 2D/3D hybrid structure, we assembled low-band-gap Sn-based perovskite solar cells with power conversion efficiency greater than 12%. The best device was among the most stable Sn-based organic-inorganic hybrid perovskite solar cells to date, keeping 90% of its initial performance at ambient condition without encapsulation, and more than 70% under continuous illumination in an N2-filled glovebox for over 1 month., Graphical Abstract, Highlights • The 2D perovskite lattice is seamlessly connected to the 3D perovskite lattice • Polymorphs of 2D perovskite were directly observed in a single perovskite film • The best device is among the most stable Sn-based perovskite solar cells to date, Materials Science; Optical Materials; Energy Materials

Surface albedo is one of the most important properties of underlying surface. However, errors still exist in the calculation of the surface albedo because of complex influencing factors. Understanding the relationship between the surface albedos in different wavebands, and soil moisture will provide theory basis for the parameterization of surface albedos. In this paper, using the data on the spectral radiation and soil moisture observation in Dunhuang, China, from August to October 2016, the spectral radiation characteristics of the underlying surface in this arid Gobi area, the variation characteristics of the surface spectral albedo and its relationship with 2-cm soil moisture were analyzed. The results show that the decrease of the angle of the sun due to seasonal change is the reason of the decrease of NIR, GR, VIS, and UV. The surface albedos in different wavebands are affected by the surface soil moisture, and they exhibit obvious anti-correlations. During the observation period, the average surface albedo of NIR, GR, VIS, and UV is 0.263, 0.230, 0.204, and 0.096, respectively, while the correlation coefficient with 2-cm soil moisture is − 0.522, − 0.678, − 0.804, and − 0.812, respectively. When solar altitude is larger than 40°, the correlation coefficients between the NIR, GR, VIS, and UV surface albedos and 2-cm soil moisture are becoming larger. And the linear regression coefficients between the NIR, GR, VIS, and UV surface albedos and 2-cm soil moisture are becoming smaller. Shorter wavelengths correspond to stronger relationships between the surface albedo and soil moisture. At longer wavelengths, the decrease in the surface albedo due to the increase in soil moisture is sharper.

The mechanisms governing variations in autumn precipitation are complicated and influenced by a number factors. This paper analyses the characteristics of autumn precipitation in China and investigates the influence of Asian polar vertex contraction on rainfall deficits in China and relevant mechanisms. Autumn precipitation decreased significantly from 1961 to 2012 in mid- and southern China, and the area of the Asia polar vortex (AAV) has decreased significantly since 1988. Asian polar vertex contraction is found to be an important factor in these autumn rainfall deficits in China through the following mechanism. Asian polar vertex contraction causes anomalously high geopotential heights in East Asia (from 25°N to 55°N) and low heights north of 65°N in the upper and lower troposphere, weakening meridional gradients in geopotential height. In the upper troposphere, the westerly and northerly winds are strengthened over high latitudes and westerly winds and the subtropical westerly jet are weakened over the East Asian mid-latitudes. In the lower troposphere, westerly winds are strengthened over high latitudes, westerly winds are weakened in East Asia and along the southern periphery of the Tibetan Plateau, and northerly winds in mid- and southern China are clearly strengthened. Hence, autumn rainfall decreases in mid- and southern China.

Wettability is a key property of a reservoir rock, which can significantly affect the distribution and transportation of fluids (gas, oil, water, etc.) in reservoir pores which are constructed with various minerals. As for sandstone reservoirs, quartz and feldspar are the common minerals of the framework. However, the study on the wettability of feldspar is much less than that of quartz probably due to the strong heterogeneity and complex composition of natural feldspar minerals. In this study, a method for measuring the contact angle of water droplet on a natural mineral surface is proposed by combining argon ion polishing technique with atomic force microscopy scanning (Ar+-AFM method). Compared with the traditional optical goniometer measurement, this method can apparently reduce the influence of heterogeneity on the wettability of K-feldspar surface and yield more consistent contact angle data.

Land surface albedo is a significant parameter for maintaining a balance in surface energy. It is also an important parameter of bare soil surface albedo for developing land surface process models that accurately reflect diurnal variation characteristics and the mechanism behind the solar spectral radiation albedo on bare soil surfaces and for understanding the relationships between climate factors and spectral radiation albedo. Using a data set of field observations, we conducted experiments to analyze the variation characteristics of land surface solar spectral radiation and the corresponding albedo over a typical Gobi bare soil underlying surface and to investigate the relationships between the land surface solar spectral radiation albedo, solar elevation angle, and soil moisture. Based on both solar elevation angle and soil moisture measurements simultaneously, we propose a new two-factor parameterization scheme for spectral radiation albedo over bare soil underlying surfaces. The results of numerical simulation experiments show that the new parameterization scheme can more accurately depict the diurnal variation characteristics of bare soil surface albedo than the previous schemes. Solar elevation angle is one of the most important factors for parameterizing bare soil surface albedo and must be considered in the parameterization scheme, especially in arid and semiarid areas with low soil moisture content. This study reveals the characteristics and mechanism of the diurnal variation of bare soil surface solar spectral radiation albedo and is helpful in developing land surface process models, weather models, and climate models.

Land surface processes take place on the interface between the earth and atmosphere, exerting significant influences on the weather and climate. Correct modeling of these processes is important to numerical weather forecast and climate prediction. In order to obtain a more thorough understanding of the land surface processes over the Gobi landscape, we evaluated the performance of the Common Land Model (CoLM) at Dunhuang station in Gansu Province of China to determine whether the model formulation, driven by observational data, is capable of simulating surface fluxes over the underlying desert surface. In comparison with the enhanced observation data collected at Dunhuang station over the period 22–28 August 2008, the results showed that the surface albedo simulated by CoLM was larger than that in the observation, and the simulated surface temperature was lower than the observed. After the measured values were used to correct the surface albedo, the solar radiation absorbed by the ground surface was more consistent with the measurements. A new empirical relationship of the surface thermal exchange coefficient rah was used to modify the thermal aerodynamic impedance. The simulated soil surface temperature became significantly closer to the observed value, and the simulated surface sensible heat as well as net radiative fluxes were also improved.

Land surface emissivity is a significant variable in energy budgets, land cover assessments, and environment and climate studies. However, the assumption of an emissivity constant is being used in Gobi broadband emissivity (GbBE) parameterization scheme in numerical models because of limited knowledge surrounding the spatiotemporal variation characteristics of GbBE. To address this issue, we analyzed the variation characteristics of GbBE and possible impact factor-surface soil moisture based on long-term continuous and high temporal resolution field observational experiments over a typical Gobi underlying surface in arid and semiarid areas in northwestern China. The results indicate that GbBE has obvious daily and diurnal variation features, especially diurnal cycle characteristics. The multi-year average of the daily average of GbBE is in the range of 0.932 to 0.970 with an average of 0.951 ± 0.008, and the average diurnal GbBE is in the range of 0.880 to 0.940 with an average of 0.906 ± 0.018. GbBE varies with surface soil moisture content. We observed a slight decrease in GbBE with an increase in soil moisture, although this change was not very obvious because of the low soil moisture in this area. Nevertheless, we think that soil moisture must be one of the most significant impact factors on GbBE in arid and semiarid areas. Soil moisture must be taken into account into the parameterization schemes of bare soil broadband emissivity in land surface models. Additional field experiments and studies should be carried out in order to clarify this issue.

This study uses the brightness temperature at the given microwave frequency (18.7 GHz) from the Microwave Radiation Imager (MWRI) on-board the Fengyun-3B (FY-3B) satellite to improve the τ-ω model by considering the radiative contribution from waterbody in the pixels over the wetland of the Yellow River source region, China. In order to retrieve vegetation optical depth (VOD), a dual-polarization slope parameter is defined to express the surface emissivity in the τ-ω model as the sum of soil emissivity and waterbody emissivity. In the regions with no waterbody, the original τ-ω model without considering waterbody impact is used to derive VOD. With use of the field observed vegetation water content (VWC) in the source region of the Yellow River during the summer of 2012, a regression relationship between VOD and VWC is established and then the vegetation parameter b is estimated. The relationship is employed to derive the spatial VWC during the entire vegetation growing period. The VOD retrieved is invalid and failed in some part of the study area by using the previous τ-ω model, while the results from the improved τ-ω model indicate that the VOD is in the range of 0.20 to 1.20 and the VWC is in the range of 0.20kg/m2 to 1.40kg/m2 in the entire source region of the Yellow River in 2012. Both VOD and VWC exhibit a pattern of low values in the west part and high values in the east part. The largest regional variations appear along the Yellow River. The comparison between the remote-sensing-estimated VWC and the ground-measured VWC gives the root mean square error of 0.12kg/m2. These assessments reveal that with considering the fractional seasonal wetlands in the source region of the Yellow River, the microwave remote sensing measurements from the FY-3B MWRI can be successfully used to retrieve the VWC in the source region of the Yellow River.

The understanding of surface spectral radiation and reflected radiation characteristics of different surfaces in different climate zones aids in the interpretation of regional surface energy transfers and the development of land surface models. This study analysed surface spectral radiation variations and corresponding surface albedo characteristics at different wavelengths as well as the relationship between 5-cm soil moisture and surface albedo on typical sunny days during the winter wheat growth period. The analysis was conducted using observational Loess Plateau winter wheat data from 2015. The results show that the ratio of atmospheric downward radiation to global radiation on typical sunny days is highest for near-infrared wavelengths, followed by visible wavelengths and ultraviolet wavelengths, with values of 57.3, 38.7 and 4.0%, respectively. The ratio of reflected spectral radiation to global radiation varies based on land surface type. The visible radiation reflected by vegetated surfaces is far less than that reflected by bare ground, with surface albedos of 0.045 and 0.27, respectively. Thus, vegetated surfaces absorb more visible radiation than bare ground. The atmospheric downward spectral radiation to global radiation diurnal variation ratios vary for near-infrared wavelengths versus visible and ultraviolet wavelengths on typical sunny days. The near-infrared wavelengths ratio is higher in the morning and evening and lower at noon. The visible and ultraviolet wavelengths ratios are lower in the morning and evening and higher at noon. Visible and ultraviolet wavelength surface albedo is affected by 5-cm soil moisture, demonstrating a significant negative correlation. Excluding near-infrared wavelengths, correlations between surface albedo and 5-cm soil moisture pass the 99% confidence test at each wavelength. The correlation with 5-cm soil moisture is more significant at shorter wavelengths. However, this study obtained surface spectral radiation characteristics that were affected by land surface vegetation coverage as well as by soil physical properties.

Understanding the land–atmosphere interactions over the semi-arid area of Loess Plateau is important due to its special climate and unique underlying surface. In this study, two years' micrometeorological and energy flux observations from the Pingliang Land Surface Process & Severe Weather Research Station, CAS were used to investigate the seasonal and interannual variations of radiation budget and energy fluxes over a rain-fed cropland in the semi-arid area of Loess Plateau, with an emphasis on the influence of rain, soil moisture and agricultural production activities (such as crop type and harvest time) on the energy partitioning as well as the surface energy balance. The results revealed large annual variations in the seasonal distribution of precipitation, which gave rise to significant seasonal and interannual variations in soil moisture. Soil moisture was the main factor affecting radiation budget and energy partitioning. There was a negatively linear relationship between the albedo and the soil moisture. The main consumer of available energy varied among months and years with an apparent water stress threshold value of ca. 0.12 m 3 m − 3 , and the evapotranspiration was suppressed especially during the growing season. On an annual scale, the largest consumer of midday net radiation was sensible heat flux in 2010–2011, while it was latent heat flux in 2011–2012, which accounted for about 35% and 40% of the net radiation, respectively. The agricultural activity altered the sensitivity and variability of albedo to soil moisture, as well as energy partitioning patterns. The surface energy budget closures during Dec. 2010–Nov. 2011 and Dec. 2011–Nov. 2012 were 77.6% and 73.3%, respectively, after considering the soil heat storage. The closure was comparable to other sites in ChinaFLUX (49% to 81% of 8 sites). The patterns of energy partitioning and the water stress threshold found in the semi-arid cropland could be used to evaluate and improve land surface models.

Complex dielectric constant (CDC) of bound water determines the accuracy of the complex dielectric constant of wet soil. According to electrical double-layer structure and dielectric properties, the bound water on clay particle surface is divided into strongly bound water and weakly bound water. Based on this classification, models for the complex dielectric constants of bound water and soil are established taking into consideration factors such as temperature, moisture, texture, and microwave frequency. The results show that the fundamental reason why the complex dielectric constant of bound water is between that of ice and free water is the adsorption force which forms the electrical double-layer structure on the surface of clay particles. Low-concentration cationic solution could exist in free soil water and was found as the reason for the higher salinity and conductivity of free soil water, as compared to the measured soil solution. Results of soil CDC model are in good agreement with measured data across a wide range of microwave frequencies and soil temperature, moisture, and texture. The absolute root mean square error analysis also shows that the soil CDC model in this paper compared to the other models is more accurate.

Methylammonium (MA)-free perovskite solar cells (PVSCs) have obtained great attention recently, owing to their superior stability. However, there are still gaps in efficiency between MA-free PVSCs and MA-containing counterparts. Their stability still needs to be further enhanced for meeting commercial standards, especially the illumination stability. Here, we incorporate Zn2+ into perovskite thin films to passivate defects, successfully achieving a champion efficiency of 20.7% and reinforcing the stability of MA-free FA0.9Cs0.1PbI3 PVSCs. This study reveals that Zn-doping can increase the grain size and contribute to modulate the crystallization process. Moreover, it is found that most of the Zn2+ aggregates at the grain boundaries passivating defects and, thus, effectively restrain the non-radiative recombination in the PVSCs. These findings provide a new way of realizing highly efficient and stable PVSCs.

Inspired by the photosynthesis process of natural plants, multifunctional transistors based on natural biomaterial chlorophyll and organic semiconductors (OSCs) are reported. Functions as photodetectors (PDs) and light-stimulated synaptic transistors (LSSTs) can be switched by gate voltage. As PDs, the devices exhibit ultrahigh photoresponsivity up to 2 × 106 A W-1 , detectivity of 6 × 1015 Jones, and Iphoto /Idark ratio of 2.7 × 106 , which make them among the best reported organic PDs. As LSSTs, important synaptic functions similar to biological synapses are demonstrated, together with a dynamic learning and forgetting process and image-processing function. Significantly, benefiting from the ultrahigh photosensitivity of chlorophyll, the lowest operating voltage and energy consumption of the LSSTs can be 10-5 V and 0.25 fJ, respectively. The devices also exhibit high flexibility and long-term air stability. This work provides a new guide for developing organic electronics based on natural biomaterials.

Almost all highly efficient perovskite solar cells (PVSCs) with power conversion efficiencies (PCEs) of greater than 22% currently contain the thermally unstable methylammonium (MA) molecule. MA-free perovskites are an intrinsically more stable optoelectronic material for use in solar cells but compromise the performance of PVSCs with relatively large energy loss. Here, the open-circuit voltage (Voc ) deficit is circumvented by the incorporation of β-guanidinopropionic acid (β-GUA) molecules into an MA-free bulk perovskite, which facilitates the formation of quasi-2D structure with face-on orientation. The 2D/3D hybrid perovskites embed at the grain boundaries of the 3D bulk perovskites and are distributed through half the thickness of the film, which effectively passivates defects and minimizes energy loss of the PVSCs through reduced charge recombination rates and enhanced charge extraction efficiencies. A PCE of 22.2% (certified efficiency of 21.5%) is achieved and the operational stability of the MA-free PVSCs is improved.

Using data collected from a specially designed experiment at the Dunhuang Station (40°10′N, 94°31′E, 1150 m) from September 2017 to September 2018, we have characterized the influences of soil moisture and solar altitude on surface spectral albedo in an arid area. The specific settings of our experiment allowed us to minimize the influences of underlying surface, cloud cover, aerosol and weather conditions, and thus highlight the influence of soil moisture and solar altitude. During the timespan of the experiment, we observed the annual mean surface albedo of global radiation (GR), ultraviolet radiation (UV), visible radiation (VIS) and near-infrared radiation (NIR) to be 0.24, 0.11, 0.24 and 0.25. A significantly negative linear correlation between surface albedo and soil moisture was identified, with the correlation coefficients between GR, UV, VIS, NIR and soil moisture being −0.68, −0.75, −0.70 and −0.61. In addition, we identified an exponential relationship between surface albedo and solar altitude. The exponential regression coefficients are −0.21, −0.077, −0.53 and −0.21, respectively. From these analyses, we derived a new two-factor parametric formula for depicting the influence of soil moisture and solar altitude on surface spectral albedo. Using observation data, we demonstrate that the formula recapitulates the real-world relationship between soil moisture, solar altitude and surface spectral albedo with little deviation. These findings may help us gain a deeper understanding of improving land surface parameterizations and have potential implications for solar energy research and applications.

In the past few years, substantial progress has been made in perovskite light-emitting devices. Both pure green and infrared thin-film perovskite light-emitting devices with external quantum efficiency over 20% have been successfully achieved. However, pure-red and blue thin-film perovskite light-emitting diodes still suffer from inferior efficiency. Therefore, the development of efficient and stable thin-film perovskite light-emitting diodes with pure-red and blue emissions is urgently needed for possible applications as a new display technology and solid-state lighting. Here, we demonstrate an efficient light-emitting diode with pure-red emission based on polymer-assisted in situ growth of high-quality all-inorganic CsPbBr0.6I2.4 perovskite nanocrystal films with homogenous distribution of nanocrystals with size 20–30 nm. With this method, we can dramatically reduce the formation temperature of CsPbBr0.6I2.4 and stabilize its perovskite phase. Eventually, we successfully demonstrate a pure-red-emission ...

In this work, a SnO

We compared the correspondence of tropopause heights over China calculated from the gridded temperature data provided by the ERA-Interim project, NCEP/NCAR Reanalysis Projects-1 (NCEP-1), and Japanese 25-year Reanalysis (JRA-25) project with the radiosonde observational data for 1979–2012. The results indicate that the annual mean ERA-Interim, NCEP-1, and JRA-25 tropopause heights are higher than observations by 203, 228, and 293 gpm, respectively. Large positive differences for the majority of subtropical China primarily contribute to this high bias. An error analysis indicates that the internal coherence of the ERA-Interim data is better than that of NCEP-1 or JRA-25. Although JRA-25 was a second-generation reanalysis, the biases of the JRA-25 and NCEP-1 data relative to the observations remain substantially larger than those of the ERA-Interim. Furthermore, a spatial and temporal comparison of trends also indicates that the ERA-Interim tropopause height changes correspond most closely to the observed trends in China. Overall, our comprehensive analysis of the three reanalysis products indicates that on both seasonal and annual bases, the ERA-Interim tropopause heights are closer to the observations than those of the NCEP-1 or JRA-25 reanalyses. Furthermore, the biases are mainly a result of the algorithm that determines the tropopause height, which is limited by the coarse vertical resolution of the input data.

Land–atmosphere interactions in the northwest arid and semi-arid areas of China are important because of their influence on energy exchange at both regional and global scales. In this paper, regular meteorological observations, as well as flux eddy covariance methods, are used to measure land–atmosphere energy exchange. Experiments were conducted over the Dunhuang Gobi, a typical arid region of northwest China, during the summer of 2008. Surface fluxes were measured directly using an eddy-correlation system, while the vertical gradients of wind and temperature were also observed at four levels using a meteorological tower. Based on the observation data, the integral mean of surface albedo over the Gobi was found to be 0.238. In addition, the mean values of momentum, heat roughness lengths, and soil thermal conductivity were, 0.045, 0.005 cm, 0.199 and 0.201 W (m K)−1, respectively. The Monin–Obukhov similarity functions for momentum and heat were analyzed and new empirical formulae were developed.

Land surface albedo is a significant parameter for maintaining a balance in surface energy. It is also an important parameter of bare soil surface albedo for developing land surface process models that accurately reflect diurnal variation characteristics and the mechanism behind the solar spectral radiation albedo on bare soil surfaces and for understanding the relationships between climate factors and spectral radiation albedo. Using a data set of field observations, we conducted experiments to analyze the variation characteristics of land surface solar spectral radiation and the corresponding albedo over a typical Gobi bare soil underlying surface and to investigate the relationships between the land surface solar spectral radiation albedo, solar elevation angle, and soil moisture. Based on both solar elevation angle and soil moisture measurements simultaneously, we propose a new two‐factor parameterization scheme for spectral radiation albedo over bare soil underlying surfaces. The results of numerical simulation experiments show that the new parameterization scheme can more accurately depict the diurnal variation characteristics of bare soil surface albedo than the previous schemes. Solar elevation angle is one of the most important factors for parameterizing bare soil surface albedo and must be considered in the parameterization scheme, especially in arid and semiarid areas with low soil moisture content. This study reveals the characteristics and mechanism of the diurnal variation of bare soil surface solar spectral radiation albedo and is helpful in developing land surface process models, weather models, and climate models., Key Points Field observation experiment of surface solar spectral radiationThe impact of solar elevation angle and soil moisture on the diurnal variation characteristics of bare soil surface albedoSolar elevation angle is a significant factor of controlling the diurnal variation characteristics of bare soil surface albedo

Complex interactions between the land surface and atmosphere and the exchange of water and energy have a significant impact on climate. The Tibetan Plateau is the highest plateau in the world and is known as “Earth’s third pole”. Because of its unique natural geographical and climatic characteristics, it directly affects China’s climate, as well as the world’s climate, through its thermal and dynamic roles. In this study, the BCCCSM1.1 model for the simulation results of CMIP5 is used to analyze the variation of the land surface processes of the Tibetan Plateau and the possible linkages with temperature change. The analysis showed that, from 1850 to 2005, as temperature increases, the model shows surface downward short-wave radiation, upward short-wave radiation, and net radiation to decrease, and long-wave radiation to increase. Meanwhile, latent heat flux increases, whereas sensible heat flux decreases. Except for sensible heat flux, the correlation coefficients of land surface fluxes with surface air temperature are all significant at the 99 % significance level. The model results indicate rising temperature to cause the ablation of ice (or snow) cover and increasing leaf area index, with reduced snowfall, together with a series of other changes, resulting in increasing upward and downward long-wave radiation and changes in soil moisture, evaporation, latent heat flux, and water vapor in the air. However, rising temperature also reduces the difference between the surface and air temperature and the surface albedo, which lead to further reductions of downward and upward short-wave radiation. The surface air temperature in winter increases by 0.93 °C/100 years, whereas the change is at a minimum (0.66 °C/100 years) during the summer. Downward short-wave and net radiation demonstrate the largest decline in the summer, whereas upward short-wave radiation demonstrates its largest decline during the spring. Downward short-wave radiation is predominantly affected by air humidity, followed by the impact of total cloud fraction. The average downward short-wave and net radiation attain their maxima in May, whereas for upward short-wave radiation the maximum is in March. The model predicts surface temperature to increase under all the different representative concentration pathway (RCP) scenarios, with the rise under RCP8.5 reaching 5.1 °C/100 years. Long-wave radiation increases under the different emission scenarios, while downward short-wave radiation increases under the low- and medium-emission concentration pathways, but decreases under RCP8.5. Upward short-wave radiation reduces under the various emission scenarios, and the marginal growth decreases as the emission concentration increases.

Thus far, most of the layered quasi-2D perovskite materials exploited in the perovskite light-emitting diodes (PeLEDs) are based on large-size monoamine cations, which forms a bilayered organic barrier between the perovskite sheets (known as the Ruddlesden-Popper (RP) phase). However, the organic spacer between the perovskite sheets can be composed of a single-layer diamine cation, for which the perovskite sheets might possess a strengthened connection due to the direct linkage of the diamine cation (referred as the Dion-Jacobson (DJ) phase). Until now, the studies of PeLEDs based on the DJ phase 2D perovskite materials are still rare. Herein, a series of DJ phase quasi-2D EDBE(MAPbBr3)n-1PbBr4 perovskites [EDBE: 2,2-(ethylenedioxy)bis(ethylammonium)] is developed and their application in PeLEDs is investigated. Interestingly, different to the broad emission of the 2D EDBEPbBr4 film, the quasi-2D film exhibited a narrow emission, indicating a decreased lattice torsion and trap states. After careful device engineering, a green light-emitting perovskite LED based on the EDBE(MAPbBr3)2PbBr4 film is demonstrated to deliver a maximum luminescence of 1903 cd m−2 and a maximum EQE of 1.06%. We note such performance is inferior to the existing RP phase 2D perovskite, which is limited by the poor thermal stability of the studied EDBE-based 2D perovskites.

The land surface energy exchange depends highly on the surface properties. Little is known of the energy balance over a typical banana plantation of humid tropics. In this study, we examine the characteristics of surface energy exchange over a typical banana field in South China during the period of May 2010 to April 2011 by using the eddy covariance and micrometeorological tower. The results showed that the diurnal and seasonal variations in surface latent heat flux were larger compared with those over the nearby grassland. The dominant energy partitioning varies with season. The latent heat flux was the main consumer of net radiation in summer, whereas the sensible heat flux was the main consumer in winter. The increasing cloud coverage and rain appear to control the surface energy balance with the development of the monsoon. Due to increased afternoon convective cloud systems in the monsoon active period, downward shortwave radiation was dramatically diminished around 14:00 pm. The annual mean Bowen ratio was 0.69, which fell within the range of other vegetated surfaces. The observed surface energy components were not closed, and the ratio of turbulent fluxes to the available energy was about 77 % in October–January and about 85 % in the other months after considering soil heat and air heat storage.