Eliminating the Burn-in Loss of Efficiency in Organic Solar Cells by Applying Dimer Acceptors as Supramolecular Stabilizers.

The meta-stable active layer morphology of organic solar cells (OSCs) is identified as the main cause of the rapid burn-in loss of power conversion efficiency (PCE) during long-term device operation. However, effective strategies to eliminate the associated loss mechanisms from the initial stage of device operation are still lacking, especially for high-efficiency material systems. Herein, the introduction of molecularly engineered dimer acceptors with adjustable thermal transition properties into the active layer of OSCs to serve as supramolecular stabilizers for regulating the thermal transitions and optimizing the crystallization of the absorber composites is reported. By establishing intimate π-π interactions with small-molecule acceptors, these stabilizers can effectively reduce the trap-state density (Nt) in the devices to achieve excellent PCEs over 19%. More importantly, the low Nt associated with an initially optimized morphology can be maintained under external stresses to significantly reduce the PCE burn-in loss in devices. This research reveals a judicious approach to improving OPV stability by establishing a comprehensive correlation between material properties, active-layer morphology, and device performance, for developing burn-in-free OSCs.

The role of interfacial donor-acceptor percolation in efficient and stable all-polymer solar cells.

Polymerization of Y6-type acceptor molecules leads to bulk-heterojunction organic solar cells with both high power-conversion efficiency and device stability, but the underlying mechanism remains unclear. Here we show that the exciton recombination dynamics of polymerized Y6-type acceptors (Y6-PAs) strongly depends on the degree of aggregation. While the fast exciton recombination rate in aggregated Y6-PA competes with electron-hole separation at the donor-acceptor (D-A) interface, the much-suppressed exciton recombination rate in dispersed Y6-PA is sufficient to allow efficient free charge generation. Indeed, our experimental results and theoretical simulations reveal that Y6-PAs have larger miscibility with the donor polymer than Y6-type small molecular acceptors, leading to D-A percolation that effectively prevents the formation of Y6-PA aggregates at the interface. Besides enabling high charge generation efficiency, the interfacial D-A percolation also improves the thermodynamic stability of the blend morphology, as evident by the reduced device "burn-in" loss upon solar illumination.

[Relationship Between Urbanization and Carbon Emissions in the Chang-Zhu-Tan Region at the County Level].

Urbanization is a major source of carbon emissions. A quantitative study on the dynamic relationship between urbanization and its morphological characteristics and carbon emissions is crucial for formulating urban carbon emission reduction policies. Based on the carbon metabolism model, the carbon emissions at the country level in Chang-Zhu-Tan from 1995 to 2020 were calculated. The Tapio decoupling model was used to explore the decoupling relationship between the carbon emissions of Chang-Zhu-Tan and urban land, and a geographically and temporally weighted regression(GTWR) model was used to analyze the impact mechanism of urban spatial morphology on carbon emissions. The following conclusions were drawn:① carbon emissions at the county level in the study area formed a clustered distribution centered on the city jurisdiction and showed a trend of diffusion from year to year. Compared with those in 1995, there were seven new high carbon emission districts in 2020, all of which belonged to Changsha. ② From 1995-2020, the research area as a whole changed from mainly strong decoupling to mainly dilated negative decoupling, and the spatial decoupling state fluctuated back and forth between the decoupling and negative decoupling. By 2020, except for the seven regions with the uncoupling state regressing, all of them reached the uncoupling state or were close to the uncoupling state. ③ Urban patch area(CA), urban patch number(NP), and patch combination degree(COHESION) were positively correlated with urban carbon emissions, whereas landscape shape index(LSI), maximum patch index(LPI), and Euclidean distance mean(ENN_MN) were negatively correlated with urban carbon emissions, and the impact of different urban form indicators on carbon emissions had significant spatial heterogeneity.

[Spatiotemporal Characteristics and Influencing Factors of Environment Emergency Incident in China from 1991 to 2018].

Research on the spatiotemporal characteristics and influencing factors of environmental emergency incidents in China in recent decades can improve the effectiveness and accuracy of risk supervision of environmental emergency incidents. Based on the data of environmental emergency incidents in 31 provincial regions in China from 1991 to 2018, this study used spatial autocorrelation analysis and a geographically and temporally weighted regression model to analyze the spatial dependence of environmental emergency incidents and the temporal and spatial heterogeneity of influencing factors. The results showed that: ① there was a significant positive spatial correlation between environmental emergency incidents during 1991-1994 and 2001-2014, and the spatial agglomeration was gradually increasing, that is, environmental emergency incidents existed in the provinces of China; clearly, the space depended on the characteristics and was not completely random. ② There was an unbalanced development pattern of environmental emergency incidents in China. The provinces with "L-L" agglomeration were concentrated in the western and northeastern regions, and the number increased and then decreased; by contrast, the ones with "H-H" agglomeration shifted from the east and south to the central and western regions, and the number increased following the decrease. The role of environmental emergency incident in different provincial regions in the spatial agglomeration was different and constantly changing. ③ The effects of various influencing factors on environmental emergency incidentshad obvious temporal and spatial heterogeneity in different periods and different provinces. The impact of the level of economic development on environmental emergency incidents was shown as a "negative-positive-negative" pattern. The impact of industrial structure on environmental emergency incidents was shown as a "negative-positive" pattern. The overall impact of pollution emissions on environmental emergency incident presented a "positive-negative-positive" pattern. Environmental letters and visits had a positive impact on the occurrence of environmental emergency incidents. The negative impact of the legal environment on environmental emergency incidents was gradually weakening. The negative impact of pollution control on environmental emergency incidents at the provincial level has gradually become apparent.

Impact of China's environmental decentralization on carbon emissions from energy consumption: an empirical study based on the dynamic spatial econometric model.

Facing the growing problem of carbon emission pollution, the scientific and reasonable division of environmental management power between governments is the premise and institutional foundation for realizing China's carbon emission reduction target in 2030. In this article, we directly assess the degree of environmental decentralization according to the allocation of environmental managers among different levels of government. By incorporating fiscal decentralization indicators, the provincial panel data and dynamic spatial econometric model are used to empirically test the impact of environmental decentralization on carbon emissions from a spatial perspective. The results show that (1) China's provincial carbon emissions have significant inertia dependence and spatial path dependence. The increase (decrease) of provincial carbon emissions will lead to the increase (decrease) of carbon emissions in neighboring regions. (2) At the national level, environmental decentralization, environmental administrative decentralization, and environmental monitoring decentralization significantly reduce China's carbon emissions, while environmental supervision decentralization and fiscal decentralization significantly increase carbon emissions. Similarly, the interaction of environmental decentralization and its decomposition indicators and fiscal decentralization also significantly promotes carbon emissions, and the impact is related to the types of environmental management decentralization. (3) The carbon emission effects of environmental decentralization in different regions are heterogeneous. The inhibition effect of environmental decentralization, environmental administrative decentralization, and environmental monitoring decentralization on carbon emissions in the western region is significantly greater than that in the eastern and central regions, but the inhibitory effect of the interaction of environmental decentralization and its decomposition index and fiscal decentralization on carbon emissions in the eastern region was significantly stronger than that in the central and western regions. The above results provide theoretical support for China to construct a differentiated carbon emission environmental management system from two aspects of regional differences and environmental management power categories.

Climatic and edaphic controls over soil δ15N in temperate grassland of northern China: A PLS-PATH analysis.

Identifying the impact path of climate and soil factors on soil δ15N is very crucial for better understanding the N turnover in soils and the integrated information about ecosystem N cycling. Many studies have showed that climate and soil variables influence the change of soil δ15N. However, most of the existing studies focused on the overall impact of factor on soil δ15N, without distinguishing between the direct and indirect effect. Although scholars have studied the relationships among temperature, precipitation, soil N, soil pH, and soil δ15N rather than estimating all the causal relationships simultaneously. To answer the above-mentioned questions, a regional-scale soil collection was conducted across a temperate grassland in northern China. Meanwhile, a PLS-PATH analysis was utilized to evaluate the direct and indirect effects of various factors on soil δ15N and to explore the causal relationships among variables. The results showed that along the transect, mean annual precipitation (MAP) and mean annual temperature (MAT) directly and significantly reduced soil δ15N, and indirectly affected soil δ15N through their effects on soil pH, soil clay, soil N and soil C/N. Soil C/N ratio has a significant direct impact on soil δ15N with a negative correlation. Soil clay, soil N content, and soil pH have a total positive effect on soil δ15N, but the total positive impact of soil pH is very weak because it has a negative indirect impact on soil δ15N by affecting soil clay, soil N and soil C/N ratio. The total influence is, in order, MAP > MAT > soil C/N > soil clay > soil N > soil pH (in absolute value). The above results will provide valuable information about ecosystem N cycle in temperate grassland of northern China.

15N Natural Abundance of C3 and C4 Herbaceous Plants and Its Response to Climatic Factors along an Agro-Pastoral Zone of Northern China.

The nitrogen isotope composition of plants (δ15N) can comprehensively reflect information on climate change and ecosystems' nitrogen cycle. By collecting common herbs and soil samples along the 400 mm isoline of mean annual precipitation (MAP) in the agro-pastoral zone of North China (APZNC) and measuring their δ15N values, the statistical characteristics of foliar δ15N of herbs and the responses of foliar δ15N to the MAP and mean annual temperature (MAT) were analyzed. The results showed that: (1) the δ15N values of all herbs investigated varied from -5.5% to 15.25%. Among them, the δ15N value range of C3 herbs (-5.5~15.00%) was wider than that of C4 herbs (-2.17~15.25%), but the average value (3.27%) of C3 herbs was significantly lower than that of C4 herbaceous plants (5.55%). This difference provides an important method for identifying plants of different photosynthetic types by nitrogen isotope technology. (2) Along the transect from northeast to southwest, the δ15N of both C3 and C4 herbs decreased with the increase in the MAP, but not significantly for C3 herbs. The inverse relationship between the nitrogen isotopic signatures of herbs and MAP is consistent with previous studies. However, the MAP in the APZNC is found to only explain a small amount of the observed variance in the δ15N herbs (C3 herbs: 10.40%; C4 herbs: 25.03%). (3) A strong negative relationship was found between δ15N of herbs and MAT across the transect (C3 herbs: -0.368%/°C; C4 herbs: -0.381%/°C), which was contrary to the global pattern and some regional patterns. There was no significant difference in the δ15N responses of two different photosynthetic herbs to temperature, but the effect of temperature on the variances of δ15N of C3 and C4 herbs was significantly greater than that of precipitation. This suggests that temperature is a key factor affecting foliar δ15N of herbs in this transect. The above findings may be of value to global change researchers studying the processes of the nitrogen cycle and gaining an insight into climate dynamics of the past.

CdS and Ag synergistically improved the performance of g-C3N4 on visible-light photocatalytic degradation of pollution.

CdS-AgO@g-C3N4 nanocomposites were successfully synthesized and characterized by XRD, N2 physical adsorption, XPS, SEM, TEM, EDX, and UV-Vis DRS (various technical means). The adsorption light range of as-prepared materials could extend to the whole visible light region with the addition of Ag. Silver can act as a bridge to facilitate the separation of electrons and holes, thereby greatly enhancing the photocatalytic activity of CdS-AgO@g-C3N4, enabling the maximum degradation efficiency of salicylic acid in water to reach 92.8% under visible light. Peroxy radical is the most important radical in the photocatalytic reaction process, followed by electron and hole, while hydroxyl radical has almost no effect. In addition, the mechanism of photocatalytic process was also explored.

Measurements of nitrogen isotope composition of plants and surface soils along the altitudinal transect of the eastern slope of Mount Gongga in southwest China.

The natural abundances of stable nitrogen isotopes in plants and soils have been viewed as recorders that can be used to reconstruct paleoclimate and ecological processes or to indicate the biogeochemical cycle of nitrogen in nature. This study systematically measured the nitrogen isotope composition (δ(15)N) in plants and surface soils along an altitudinal transect of elevation range of 1200 to 4500 m on the eastern slope of Mount Gongga in southwest China. The influences of photosynthetic pathways on plant δ(15)N as well as the effects of temperature and precipitation on δ(15)N altitudinal trends in plants and surface soils are discussed. Across this altitude transect, the δ(15)N values of C(3) and C(4) plants on Mount Gongga range between -9.87‰ and 7.58‰ with a mean value of -1.33‰, and between -3.98‰ and 4.38‰ with a mean value of -0.25‰, respectively. There is an evident δ(15)N difference between C(3) plants and C(4) plants. If, however, you only compare C(4) plants with those C(3) plants growing at the same altitudinal range, no significant difference in δ(15)N exists between them, suggesting that photosynthetic pathway does not have an influence on the plant δ(15)N values. In addition, we found that C(3), C(4) plants and surface soil (0-5 cm depth) all trend significantly towards more negative δ(15)N with increasing elevation. Furthermore, this study shows that the mean annual temperature and the mean annual precipitation positively and negatively correlate with δ(15)N in C(3) and C(4) plants, respectively. This indicates that precipitation and temperature are the main controlling factors of the δ(15)N variation in plants with altitude. We propose that lower δ(15)N values of plants and soils at higher altitude should be attributed to lower mineralization and lower net nitrification rates induced by low temperature and abundant rainfall.

[Analysis of Multi-scale Spatio-temporal Differentiation Characteristics of PM2.5 in China from 2011 to 2017].

It is of great significance for joint prevention and control of air pollution to understand the spatial and temporal differentiation characteristics and regional driving factors of PM2.5 in China. In this study, from a multi-scale perspective, the spatial pattern analysis and geographical detectors are used to explore the spatial and temporal distribution pattern and causes of PM2.5 pollution in China mainland from 2011 to 2017. The results show that:① the annual average PM2.5 concentration is relatively stable from 2011 to 2017, and there is no obvious trend. The change characteristics of regional PM2.5 are similar to those of national PM2.5, showing a "W" shaped fluctuation. Overall, the order of pollution degree from high to low is:central, eastern, western, and northeastern. ② From the spatial pattern analysis results, we can see that the high-value cluster mainly appears in east China, middle China, and southwest of Xinjiang, while the low-value cluster appears in Qinghai-Tibet, Yunnan, Guizhou, Plateau, and Daxinganling regions. ③ The results of geographic detector analysis show that the population factor is the leading factor nationally; meanwhile, the industrial, energy consumption, and traffic factors all contribute to the distribution pattern of PM2.5 in varying degrees. Regionally, besides the population factor, the proportion of secondary production and urban green space rate have the greatest impact on the northeast, the industrial smoke and dust and road area in the east, and the total industrial electricity and buses in the central area. The impact of social and economic factors does not significantly affect the PM2.5 in the western region.