Tungstate-mediated In-situ Passivation of Grain Boundary Grooves in Perovskite Solar Cells.

Possessed with advantageous optoelectronic properties, perovskites have boosted the rapid development of solution-processed solar cells. The performance of perovskite solar cells (PSCs) is significantly weakened by the carrier loss at grain boundary grooves (GBGs); however, it receives limited attention and there lacks effective approach to solve this issue. Herein, for the first time, we constructed the tungstate/perovskite heterointerface via a "two step" in situ reaction approach that provides effective defect passivation and ensures efficient carrier dynamics at the GBGs. The exposed perovskite at grain boundaries is converted to wide-band-gap PbWO4 via an in-situ reaction between Pb2+ and tungstate ions, which passivate defects due to the strong ionic bonding. Moreover, recombination loss is further suppressed via the heterointerface energetics modification based on an additional transformation from PbWO4 to CaWO4 . PSCs based on this groove modification strategy showed good universality in both normal and inverted structure, with an improved efficiency of 23.25 % in the n-i-p device and 23.33 % in the p-i-n device. Stable power output of the modified device could maintain 91.7 % after around 1100 h, and the device efficiency could retain 92.5 % after aging in air for around 2110 h, and 93.1 % after aging at 85 °C in N2 for 972 h.

Metabolomics analysis of the effect of acidification on rhizosphere soil microecosystem of tea tree.

Acidification can seriously affect the growth of tea trees and the yield and quality of tea leaves. In this study, we analyzed the effects of acidification on the physicochemical properties, microorganisms and metabolites of tea rhizosphere soils with different pH values, and the results showed that with the increase of soil pH, the organic matter content, cation exchange capacity, microbial biomass carbon, microbial biomass nitrogen, microbial respiration intensity, bacterial number and actinomyces number in tea rhizosphere soil all showed an increasing trend, while the fungi number decreased. The results of soil metabolite analysis showed that 2376, 2377 and 2359 metabolites were detected in tea rhizosphere soil with pH values of 3.29, 4.74 and 5.32, respectively, and the number of similar compounds reached 2331, accounting for more than 98%. The results of soil metabolite content analysis showed that with the increase of soil pH, the total contents of metabolite of tea rhizosphere soil increased significantly. The results of correlation analysis between physicochemical indexes of soil and microorganisms and soil metabolites showed that physicochemical indexes of soil and microorganisms were significantly correlated with 221 soil metabolites, among which 55 were significantly positively correlated and 166 were significantly negatively correlated. Based on correlation interaction network analysis, 59 characteristic compounds were obtained and divided into 22 categories, among which 7 categories compounds showed a significant increasing trend with the increase of soil pH, while the other 15 categories compounds showed the opposite trend. Based on the functional analysis of characteristic metabolites, this study found that with the increase of soil pH in tea rhizosphere, the diversity and number of soil microorganisms increased, and the cyclic ability of C and N of tea rhizosphere soil was enhanced, which in turn might lead to the enhancement of resistance of tea tree and promote the growth of tea tree.

Effect of processing on aroma intensity and odor characteristic of Shuixian (Camellia sinensis) tea.

Processing is extremely important for the formation of aroma characteristic of tea leaves. In this study, the effects of processing on the content of volatile compounds, aroma intensity and odor characteristic of Shuixian tea were analyzed. The results showed that the content of volatile compounds in Shuixian tea increased significantly after processing, among which terpenoids and esters were the highest. There were 18 key compounds constituting the aroma characteristics of Shuixian tea, among which geraniol and nerol were the most important compounds, which contributed 96.28% to the aroma of Shuixian tea. The odor characteristics of Shuixian tea were mainly floral and fruity and the contribution of floral mainly came from geraniol, while fruity mainly came from nerol. Geraniol and nerol compounds increased rapidly after the withering process of tea leaves. This study provided an important reference for the improvement of processing technology and quality enhancement of Shuixian tea.

Ultralow Tip-Force Driven Sizable-Area Domain Manipulation through Transverse Flexoelectricity.

Deterministic control of ferroelectric domain is critical in the ferroelectric functional electronics. Ferroelectric polarization can be manipulated mechanically with a nano-tip through flexoelectricity. However, it usually occurs in a very localized area in ultrathin films, with possible permanent surface damage caused by a large tip-force. Here it is demonstrated that the deliberate engineering of transverse flexoelectricity offers a powerful tool for improving the mechanical domain switching. Sizable-area domain switching under an ultralow tip-force can be realized in suspended van der Waals ferroelectrics with the surface intact, due to the enhanced transverse flexoelectric field. The film thickness range for domain switching in suspended ferroelectrics is significantly improved by an order of magnitude to hundreds of nanometers, being far beyond the limited range of the substrate-supported ones. The experimental results and phase-field simulations further reveal the crucial role of the transverse flexoelectricity in the domain manipulation. This large-scale mechanical manipulation of ferroelectric domain provides opportunities for the flexoelectricity-based domain controls in emerging low-dimensional ferroelectrics and related devices.

Electrical and magnetic anisotropies in van der Waals multiferroic CuCrP2S6.

Multiferroic materials have great potential in non-volatile devices for low-power and ultra-high density information storage, owing to their unique characteristic of coexisting ferroelectric and ferromagnetic orders. The effective manipulation of their intrinsic anisotropy makes it promising to control multiple degrees of the storage "medium". Here, we have discovered intriguing in-plane electrical and magnetic anisotropies in van der Waals (vdW) multiferroic CuCrP2S6. The uniaxial anisotropies of current rectifications, magnetic properties and magnon modes are demonstrated and manipulated by electric direction/polarity, temperature variation and magnetic field. More important, we have discovered the spin-flop transition corresponding to specific resonance modes, and determined the anisotropy parameters by consistent model fittings and theoretical calculations. Our work provides in-depth investigation and quantitative analysis of electrical and magnetic anisotropies with the same easy axis in vdW multiferroics, which will stimulate potential device applications of artificial bionic synapses, multi-terminal spintronic chips and magnetoelectric devices.

Effects of Long-Term Use of Organic Fertilizer with Different Dosages on Soil Improvement, Nitrogen Transformation, Tea Yield and Quality in Acidified Tea Plantations.

In this study, sheep manure fertilizers with different dosages were used for five consecutive years to treat acidified tea plantation soils, and the effects of sheep manure fertilizer on soil pH value, nitrogen transformation, and tea yield and quality were analyzed. The results showed that soil pH value showed an increasing trend after a continuous use of sheep manure fertilizer from 2018 to 2022. After the use of low dosage of sheep manure fertilizer (6 t/hm2-15 t/hm2), tea yield, the content of tea quality indicators (tea polyphenols, theanine, amino acid, and caffeine) and soil ammonium nitrogen content, ammoniating bacteria number, ammoniating intensity, urease activity and protease activity showed increasing trends and were significantly and positively correlated to soil pH value, while the related indexes showed increasing and then decreasing trends after the use of high dosage of sheep manure fertilizer (18 t/hm2). Secondly, the nitrate nitrogen content, nitrifying bacteria number, nitrifying intensity, nitrate reductase activity, and nitrite reductase activity showed decreasing trends after the use of low dosage of sheep manure fertilizer and showed significant negative correlations with soil pH value, while the related indexes showed decreasing trends after the use of high dosage of sheep manure and then increased. The results of principal component and interaction analysis showed that the effects of sheep manure fertilizers with different dosages on tea yield and quality were mainly based on the transformation ability of ammonium nitrogen and nitrate nitrogen in the soil, and the strong transformation ability of ammonium nitrogen and the high ammonium nitrogen content in the soil were conducive to the improvement of tea yield and quality, and vice versa. The results of topsis comprehensive evaluation and analysis showed that the most influential effect on the fertilization effect was the ammonium nitrogen content in the soil and long-term treatment with 15 t/hm2 of sheep manure fertilizer had the highest proximity to the best fertilization effect. This study provided an important practical basis for the remediation and fertilizer management in acidified tea plantation soils.

Improvement of soil acidification in tea plantations by long-term use of organic fertilizers and its effect on tea yield and quality.

Soil acidification in tea plantation seriously reduced the yield and quality of tea. It was an effective method to use organic fertilizer for acidified soil remediation to ensure tea yield and quality. In this study, different fertilizers were used to treat the acidified tea plantation soils for 4 consecutive years to analyze the remediation effect of different fertilizers on acidified soil and their effects on tea yield and quality. The results showed that during the period of 2017-2021, the soil pH value of tea plantation (S1) with long-term use of chemical fertilizer decreased continuously, from 3.07 to 2.82. In the tea plantation (S2), the soil pH value was stable between 4.26 and 4.65 in the combination of organic fertilizer and chemical fertilizer for a long time. The tea plantation (S3) with long-term use of organic fertilizer has a stable soil pH value between 5.13 and 5.33, which is most suitable for the growth of tea trees. The analysis results of tea yield and quality indicators (tea polyphenols, theanine, amino acids, caffeine, catechin components) showed that after long-term use of chemical fertilizer in S1 tea plantation, soil pH value decreased continuously, soil acidification intensified, tea tree growth was hindered, and tea yield and quality decreased continuously. S2 tea plantation used some organic fertilizer in combination with chemical fertilizer for a long time, the soil pH value gradually improved, soil acidification weakened, and tea yield and quality improved steadily. After long-term use of organic fertilizer in S3 tea plantation, soil acidification was significantly improved, which was conducive to the normal growth of tea trees and the yield and quality of tea reached the maximum. The results of interaction analysis showed that the long-term use of chemical fertilizer had a negative effect on the growth of tea trees, and the combination of organic fertilizer and chemical fertilizer improved the growth of tea trees to some extent, but the effect was poor, while the long-term use of organic fertilizer was the most beneficial to the growth of tea trees and most conducive to ensuring the yield and quality of tea. This study provides important practical significance for the remediation and fertilizer regulation of acidified tea plantation soils. In the process of field experiment, climate is a variable factor, and attention should be paid to the effect of climate change on fertilization efficiency in subsequent experiment.

Strain Modulation for Light-Stable n-i-p Perovskite/Silicon Tandem Solar Cells.

Perovskite/silicon tandem solar cells are promising to penetrate photovoltaic market. However, the wide-bandgap perovskite absorbers used in top-cell often suffer severe phase segregation under illumination, which restricts the operation lifetime of tandem solar cells. Here, a strain modulation strategy to fabricate light-stable perovskite/silicon tandem solar cells is reported. By employing adenosine triphosphate, the residual tensile strain in the wide-bandgap perovskite absorber is successfully converted to compressive strain, which mitigates light-induced ion migration and phase segregation. Based on the wide-bandgap perovskite with compressive strain, single-junction solar cells with the n-i-p layout yield a power conversion efficiency (PCE) of 20.53% with the smallest voltage deficits of 440 mV. These cells also maintain 83.60% of initial PCE after 2500 h operation at the maximum power point. Finally, these top cells are integrated with silicon bottom cells in a monolithic tandem device, which achieves a PCE of 26.95% and improved light stability at open-circuit.