Re-identifying farmland carbon neutrality gap under a new carbon counting and the framework of regional interactions in China.

The farmland ecosystem, with its numerous material cycles and energy flows, is an important part of the carbon cycle in terrestrial ecosystems. Focusing on the carbon neutrality of farmland is meaningful for mitigating global warming and serving national low-carbon strategies. This study enriches the carbon accounting items of farmland and establishes a new research framework to check the carbon neutrality of farmland from the aspect of regional interactions and, subsequently, the inequality among China's provinces. The results revealed that there is still a great gap in the capability of China's farmland to reach carbon neutrality, with a gap value of up to 10,503 × 104 t C. All of the provinces presented net carbon emissions, and the per unit area carbon neutrality gaps showed spatial regularity decreasing from the coastal regions to the inland areas. Anthropogenic carbon emissions on farmland played a dominant role compared with soil organic carbon. Five provinces had reduced interior-regional carbon emissions through grain trade, and the amounts were especially high for developed regions, such as Guangdong, Zhejiang, Beijing, Shanghai and Jiangsu. Sixteen provinces gained external carbon emissions through trade; these were the less developed regions located mainly in the north, such as Inner Mongolia, Hebei, Jilin, Heilongjiang and Xinjiang. Under regional inequality, 15 provinces added to the net amount of the carbon emissions generated in external regions, with China's megacities adding the highest percentage, especially Beijing, with 389.95 % compared with its original emissions. Inequality showed that most provinces had a moderate status. Sichuan and Hunan experienced weak advantages, and six provinces had disadvantages. Therefore, constructing compensation and trade-based rights and responsibilities traceability mechanisms is important.

[Spatiotemporal Evolution Characteristics of Carbon Sources and Carbon Sinks and Carbon Balance Zoning in the Yangtze River Delta Region].

Mastering the spatiotemporal evolution laws of carbon sources and sinks is of great significance to promote the coordinated development of regional low-carbon, improve the science of carbon reduction and sink increase policies, and realize the goal of "double carbon." Taking 41 cities in the Yangtze River Delta Region as the research object, this study analyzed the spatiotemporal evolution characteristics of carbon sources and sinks in the Yangtze River Delta Region from 2000 to 2020 and conducted the carbon balance zoning. The results were as follows： ① The carbon emissions increased rapidly in the Yangtze River Delta Region from 2000 to 2011 but with some fluctuations after 2011. Carbon sinks increased slowly in the Yangtze River Delta Region from 2000 to 2020. The regional differences in carbon emissions and carbon sinks were significant, and the spatial pattern was relatively stable. ② The carbon compensation rate in the Yangtze River Delta Region showed a downward trend, and the carbon productivity, energy utilization efficiency, and carbon ecological support capacity were constantly enhanced. Interregional differences were the main source of carbon compensation rate in the Yangtze River Delta Region. Both the carbon compensation rate and carbon ecological support coefficient showed a spatial pattern of "high in the west and low in the east, high in the south and low in the north." The areas with high carbon economy contributive coefficient were concentrated in the central and southern areas of the Yangtze River Delta regions, and the areas with low carbon economy contributive coefficient were concentrated in Anhui Province. ③ Based on the carbon economy contributive coefficient and the carbon ecological support coefficient, cities in the Yangtze River Delta Region were classified into low-carbon maintenance areas, economic development areas, carbon sink development areas, and comprehensive optimization areas. Recommendations were proposed for each category of cities in order to promote the coordinated development of regional low-carbon and realize the goal of "double carbon".

Inequality characteristics and influencing factors of CO2 emissions per capita in Jiangsu Province, China.

Analyzing the inequality characteristics and influencing factors of CO2 emissions per capita (CEPC) is conducive to balancing regional development and CO2 emissions reduction. This study applied the Gini coefficient and Theil index to investigate the CEPC inequalities during 2005-2017 at the county level in Jiangsu Province, China. Considering the spatial spillover and interaction effects, the factors influencing CEPC were analyzed by a hierarchical spatial autoregressive model. The results showed that the inequalities in CEPC first increased and then decreased at the inter-regional, and inter-county levels. The spatial pattern of CEPC was stable, and there was a significantly positive spatial autocorrelation of CEPC at the county level. The High-High type counties were mainly located in Sunan (southern Jiangsu). The spatial interaction effects of the CEPC between the prefecture and county levels indicated that governments at the prefecture level should integrate their county governments to reduce the CEPC. Moreover, carbon intensity, GDP per capita, land urbanization, and industrial structure play an important role in reducing CEPC. Our findings provide a scientific basis for formulating reasonable and effective carbon emission reduction policies.

Experimental Study on the Tridacna squamosa Shell: Distinctive Structure and Mechanical Behavior.

Tridacna squamosa, Lamarck, 1819 (Bivalvia Cardiida Cardiidae, known as the fluted giant clam) is one of the largest-sized bivalve shells, which is equipped with a strong and tough bioceramic shell to effectively protect itself from the attack of predators. To better understand the mechanical defense mechanism, the relationship between the microstructure, composition, and mechanical properties of the Tridacna squamosa shell was investigated. We find that the Tridacna squamosa shell is composed of aragonite CaCO3 and a small portion of organic matter, which are well-arranged, assembling a multiscale, inhomogeneous, and anisotropic structure. Three levels of microstructure units are identified, including the smallest aragonite rods, medium sheets, and block-like lamellae. Such multiscale structures are the main contributor to creating abundant fracture surfaces much larger than the case for single mineral components, leading to multiple toughening mechanisms observed in Vickers indentation experiments, such as pulled-out of mineral platelet and crack deflection. The material inhomogeneity in the cross-sectional direction indicates that the material is stronger at the inner layer than that at the outer layer, which also facilitates an effective defense against the predator attack. This study may provide insights into the design of biomaterials with the desired mechanical properties.

Fabrication of Biologically Inspired Electrospun Collagen/Silk fibroin/bioactive glass composited nanofibrous scaffold to accelerate the treatment efficiency of bone repair.

Bone disease and disorder treatment might be difficult because of its complicated nature. Millions of patients each year need bone substitutes that may help them recover quickly from a variety of illnesses. Synthetic bone replacements that mirror the structural, chemical, and biological features of bone matrix structure will be very helpful and in high demand. In this research, the inorganic bioactive glass nanoparticles matrixed with organic collagen and silk fibroin structure (COL/SF/CaO-SiO2) were used to create multifunctional bone-like fibers in this study, which we describe here. The fiber structure is organized in a layered fashion comparable to the sequence in which apatite and neo tissue are formed. The amino groups in COL and SF combined with CaO-SiO2 to stabilize the resulting composite nanofiber. Morphological and functional studies confirmed that crystalline CaO-SiO2 nanoparticles with average sizes of 20 ± 5 nm are anchored on a 115 ± 10 nm COL/SF nanofiber matrix. X-ray photoelectron spectroscopic (XPS) results confirmed the presence of C, N, O, Ca, and Si in the composite fiber with an atomic percentage of 59.46, 3.30, 20.25, 3.38 and 13.61%. respectively. The biocompatibility examination with osteoblast cells (Saos-2) revealed that the CAL/SF/CaO-SiO2 composite nanofiber had enhanced osteogenic activity. Finally, when the CAL/SF/CaO-SiO2 composite nanofiber scaffolds were used to treat an osteoporotic bone defect in a rat model, the composite nanofiber scaffolds significantly promoted bone regeneration and vascularization. This novel fibrous scaffold class represents a potential breakthrough in the design of advanced materials for complicated bone regeneration.

Fabrication of porous gehlenite coating on Al2O3-ZrO2-SiC composite ceramics and its in vitro biological activities.

Porous gehlenite coatings on Al2O3-ZrO2-SiC composite ceramics were prepared by electro-spraying technique combined with reactive sintering method. The influences of gehlenite coating on the mechanical property of the ceramics and biological activity of the coating were investigated. The results indicated that the gehlenite coating has limited influences on flexural strength and fracture toughness of the ceramics, and the coating has elastic modulus of 82 GPa, hardness of 2.2 GPa, and adhesive strength of 1512 mN, suggesting its potential application in load-bearing ceramic implants. Simulated body fluid soaking test, CCK-8 and alkaline phosphatase activity assay demonstrated that the porous gehlenite coating has strong mineralization ability, which promotes proliferation and differentiation of MC3T3-E1 cells. These excellent biological performances can be attributed to the synergistic effect of the porous surface of the coating and its release of Ca2+ and Si4+.

Transition Metal Engineering of Molybdenum Disulfide Nanozyme for Biomimicking Anti-Biofouling in Seawater.

Nature has evolved diverse strategies to battle surface biofouling colonization and thus provides us novel insights into designing and developing advanced nontoxic antibiofouling materials and technologies. Mimicking the defense mechanisms of natural haloperoxidases in marine algae in response to biofilm colonization, here we show that the less active MoS2 shows efficient haloperoxidase-mimicking activity through judicious transition metal engineering. Cobalt-doped MoS2 (Co-MoS2) displays an excellent haloperoxidase-mimicking performance in catalyzing the Br- oxidation into germicidal HOBr, roughly 2 and 23 times higher than the nickel-doped MoS2 and pristine MoS2, respectively. Accordingly, Co-MoS2 shows an outstanding antimicrobial effect against drug-resistant bacteria and antibiofouling performance in real field tests in marine environments. The realization of robust haloperoxidase-mimicking activity of MoS2 via metal engineering may open a new avenue to design highly active transition metal dichalcogenides for antibacterial and antibiofouling applications.

Network Pharmacology Combined with Molecular Docking and Experimental Verification Reveals the Bioactive Components and Potential Targets of Danlong Dingchuan Decoction against Asthma.

BACKGROUND: Danlong Dingchuan Decoction has a definite effect in the clinical treatment of asthma. This study aimed to explore the material and molecular biological basis of Danlong Dingchuan Decoction in treating asthma through network pharmacology combined with animal experiments. MATERIALS AND METHODS: First, the chemical constituents of Danlong Dingchuan Decoction were screened from the Traditional Chinese Medicine Systematic Pharmacology Analysis Platform (TCMSP) and the Traditional Chinese Medicine and Chemical Composition Database. Literature reports on asthma targets were obtained from the Online Mendelian Inheritance in Man (OMIM), Therapeutic Targets Database (TTD), and other databases. Then, the protein-protein interaction network was constructed according to the matching results of Danlong Dingchuan Decoction and asthma targets. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed by the Database for Annotation, Visualization, and Integrated Discovery (DAVID). Finally, the interaction between the active compounds of Danlong Dingchuan Decoction and key targets was simulated using molecular docking. In animal experiments, ovalbumin was used to induce asthma in mice. After treating the mice by oral gavage administration of Danlong Dingchuan Decoction, the expression levels of tumor necrosis factor-α (TNF-α) and interleukin-1ß (IL-1ß) were detected in the lung tissue of the mice by enzyme-linked immunosorbent assay kit, whereas TLR4 mRNA expression was detected by quantitative reverse transcription-polymerase chain reaction. RESULTS: A total of 247 active compounds and 155 potential targets were obtained. Enrichment analysis showed that quercetin, xanthine, lysine, kaempferol, ß-sitosterol, and four other active compounds were the main components of Danlong Dingchuan Decoction; IL-6, TNF, CXCL8, VEGFA, MAPK3, IL-10, PTGS2, IL-1ß, IL-4, and TLR4 were the potential targets for therapy. KEGG analysis showed that the cAMP signaling pathway, cGMP-PKG signaling pathway, NF-κB signaling pathway, and PI3K-Akt signaling pathway might play an important role in treating asthma. Molecular docking analysis showed that quercetin combined well with TNF, CXCL8, and TLR4. Animal experiments showed that Danlong Dingchuan Decoction effectively reduced the expression levels of TNF-α, IL-4, TGF-ß1, IL-6, IL-8, and IL-1ß in the lung tissue of asthmatic mice and inhibited TLR4 mRNA expression. CONCLUSIONS: Danlong Dingchuan Decoction may act on key targets (such as IL-6, TNF, CXCL8, VEGFA, and MAPK3) with key active ingredients (such as quercetin, xanthine, lysine, kaempferol, and ß-sitosterol) to reduce the expression levels of IL-4, IL-6, IL-8, and other Th2 cytokines. This may be the mechanism by which Danlong Dingchuan Decoction reduces airway inflammation and treats asthma mediated by Th2 cytokines.

Accelerated Chemical Thermodynamics of Uranium Extraction from Seawater by Plant-Mimetic Transpiration.

The extraction of uranium from seawater, which is an abundant resource, has attracted considerable attention as a viable form of energy-resource acquisition. The two critical factors for boosting the chemical thermodynamics of uranium extraction from seawater are the availability of sufficient amounts of uranyl ions for supply to adsorbents and increased interaction temperatures. However, current approaches only rely on the free diffusion of uranyl ions from seawater to the functional groups within adsorbents, which largely limits the uranium extraction capacity. Herein, inspired by the mechanism of plant transpiration, a plant-mimetic directional-channel poly(amidoxime) (DC-PAO) hydrogel is designed to enhance the uranium extraction efficiency via the active pumping of uranyl ions into the adsorbent. Compared with the original PAO hydrogel without plant-mimetic transpiration, the uranium extraction capacity of the DC-PAO hydrogel increases by 79.33% in natural seawater and affords the fastest reported uranium extraction average rate of 0.917 mg g-1 d-1 among the most state-of-the-art amidoxime group-based adsorbents, along with a high adsorption capacity of 6.42 mg g-1 within 7 d. The results indicate that the proposed method can enhance the efficiency of solar-transpiration-based uranium extraction from seawater, particularly in terms of reducing costs and saving processing time.

Effect of Accelerators on the Workability, Strength, and Microstructure of Ultra-High-Performance Concrete.

The preparation of ultra-high-performance concrete (UHPC) with both high-early-strength and good workability contributes to further promotion of its development and application. This study investigated the effects of different accelerators (SM, alkaline powder accelerator; SF, alkaline powder accelerator containing fluorine; and AF, alkali-free liquid accelerator containing fluorine) on the workability and strength properties of UHPC. The microstructure of UHPC was also characterized by using XRD and SEM. Several dosage levels of accelerators (2%, 4%, 6%, and 8% by mass) were selected. The results indicate that the setting time and fluidity of UHPC are gradually decreased with an increase in accelerators dosage. Compared with fluorine-containing SF/AF, fluorine-free SM evidently facilitates UHPC early strength gain speed. However, the fluorine-containing accelerators have a higher 28 d strength ratio, especially AF. The maximum compressive and flexural strength ratios are obtained at a dosage of 6%, which are 95.5% and 98.3%, respectively. XRD and SEM tests further reveal the effect of different accelerators on the macroscopic properties of UHPC from the micro level.

Synthesis of boron carbonitride nanosheets using for delivering paclitaxel and their antitumor activity.

As a structural analog of graphene and boron nitride, hexagonal boron carbonitride nanosheets (BCNNSs) are supposed to be a potential drug deliverer. In the present work, an improved solid-state reaction method combined with ultrasonic exfoliating was reported for preparing BCNNSs. Vapor-solid (VS) mechanism was proposed to be responsible for the formation of BCNNSs. The BCNNSs were further modified by DSPE-mPEG-5000 to improve their dispersion in aqueous solution. It was found that the BCNNSs-PEG nanocomplex could be efficiently taken in by MDA-MB-231 breast cancer cells evidenced by inverted fluorescence microscopy. The PEGylated BCNNSs showed an outstanding ability to load paclitaxel through π-π interaction and hydrophobic interaction, and BCNNSs-PEG-loaded paclitaxel presented higher cytotoxicity in comparison with free paclitaxel. BCNNSs may become a promising candidate for delivering paclitaxel and other hydrophobic drugs.

Gamma-phase CsPbBr3 perovskite nanocrystals/polymethyl methacrylate electrospun nanofibrous membranes with superior photo-catalytic property.

Gamma-phase cesium lead tri-bromide perovskite nanocrystals (γ-CsPbBr3 NCs) possess potentially photo-catalytic degradation ability and long-term stability. However, their serious aggregation issue decreases their active surface area, and the recombination of photo-generated hole-electron pairs weakens their photo-catalytic property. Furthermore, these NCs can be easily absorbed on the surface of dyes [e.g., methylene blue (MB)] or dissolved in the dye solution during the photo-catalytic degradation process, thus reducing the amount of γ-CsPbBr3 NCs and their photo-catalytic degradation ability. Besides, the residual γ-CsPbBr3 NCs in the photo-catalytic degradation products also present the toxicity issue (containing Pb) and are hazardous to the ecological environment and human health. In the present study, we fabricated γ-CsPbBr3 NCs/polymethyl methacrylate electrospun nanofibrous membranes (γ-CsPbBr3 NCs/PMMA ENMs) by using electrospinning technology to solve the above problems. It is found that the synthesized γ-CsPbBr3 NCs/PMMA ENMs show a large surface area and the abundant functional groups on their surfaces, which are benefit for forming multiple kinds of chemical bonding effect between γ-CsPbBr3 NCs and PMMA ENMs. In addition, γ-CsPbBr3 NCs could disperse homogeneously in or on the surface of PMMA ENMs. These abundant chemical bonds and homogeneous distributions of γ-CsPbBr3 NCs on the surface of PMMA ENMs can significantly decrease the recombination of photo-generated hole-electron pairs and toxicity issue of γ-CsPbBr3 NCs during the photo-catalytic degradation process. Exhilaratingly, γ-CsPbBr3 NCs/PMMA ENMs could maintain a superior photo-catalytic degradation ability toward various dyes and reveal a high photo-catalytic degradation efficiency of 99.18% in 60 min for MB.

Structural and mechanical evolution of Tridacna gigas during permineralization.

Mollusk shells have highly complex hierarchical structures and unique mechanical properties, which have been widely studied, especially in fresh shells. However, few studies have revealed differences in the structure-property correlations of shells during the permineralization process, which occurs after organism death. To better understand the effect of permineralization on the microstructure and mechanical properties of shells, this study investigated and compared the compositions, microstructures, and mechanical properties of Tridacna gigas and permineralized J-Tridacna gigas. The results showed that permineralized J-Tridacna gigas possessed coarsened aragonite minerals, less anisotropy and organic matter, and higher hardness and strength than Tridacna gigas. The toughening mechanisms of Tridacna gigas, including crack deflection, aragonite platelet pull-out, and mineral bridges, were discovered during Vickers hardness tests. Moreover, the permineralization mechanism comprised three main steps: organic matter dissolution, aragonite plate compaction, and recrystallization. This work further elaborates the permineralization mechanism, which can help increase the crystal size and improve the strength and hardness of materials. Moreover, this study provides valuable insights into the design of bioinspired advanced materials with outstanding hardness and strength.

Loading Auristatin PE onto boron nitride nanotubes and their effects on the apoptosis of Hep G2 cells.

Auristatin PE (PE) as an anti-microtubule agent possesses good anticancer activity. However, the poor target effect and strong side effect limit the clinical application of PE. Boron nitride nanotubes (BNNTs) represent an outstanding carrier candidate providing a wise choice for liver-targeted drug delivery. A drug delivery system based on BNNTs and PE (BNNTs-PE) against liver cancer cells was designed and constructed in this study. Firstly, BNNTs were prepared and hydroxylated, subsequently, PE was loaded onto BNNTs by noncovalent conjugation and was stable at neutral pH but released at pH 4.49. It was found that BNNTs-PE demonstrates an enhanced anticancer activity against Hep G2 cells in comparison with free PE. BNNTs-PE kills cancer cells in a manner of mitochondria-mediated apoptosis pathway through reducing the mitochondrial membrane potential, activating caspase cascade. This BNNTs-PE system may be very promising for the treatment of liver cancer in the future.

Perovskite/Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] Bulk Heterojunction for High-Efficient Carbon-Based Large-Area Solar Cells by Gradient Engineering.

The performance of low-temperature carbon-based perovskite solar cells (C-PSCs) with high commercial potential was hampered by the inferior interface between the absorber and carbon electrode. In this work, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) was dissolved in an antisolvent for spin-coating perovskite (CH3NH3PbI3, MAPI) films, which was applied to modify both the MAPI films and the interface between the MAPI layer and carbon electrode by gradient engineering. Finally, the C-PSCs based on MAPI-PTAA gradient bulk heterojunction films achieved a power conversion efficiency of 13.0% with an active area of 1 cm2, 26% higher than that of pristine MAPI cells, because of the passivated trap states, accelerated hole extraction, and improved crystalline properties in absorber films.

Efficiently Improving the Stability of Inverted Perovskite Solar Cells by Employing Polyethylenimine-Modified Carbon Nanotubes as Electrodes.

Inverted perovskite solar cells (PSCs) have been becoming more and more attractive, owing to their easy-fabrication and suppressed hysteresis, while the ion diffusion between metallic electrode and perovskite layer limit the long-term stability of devices. In this work, we employed a novel polyethylenimine (PEI) modified cross-stacked superaligned carbon nanotube (CSCNT) film in the inverted planar PSCs configurated FTO/NiO x/methylammonium lead tri-iodide (MAPbI3)/6, 6-phenyl C61-butyric acid methyl ester (PCBM)/CSCNT:PEI. By modifying CSCNT with a certain concentration of PEI (0.5 wt %), suitable energy level alignment and promoted interfacial charge transfer have been achieved, leading to a significant enhancement in the photovoltaic performance. As a result, a champion power conversion efficiency (PCE) of ∼11% was obtained with a Voc of 0.95 V, a Jsc of 18.7 mA cm-2, a FF of 0.61 as well as negligible hysteresis. Moreover, CSCNT:PEI based inverted PSCs show superior durability in comparison to the standard silver based devices, remaining over 85% of the initial PCE after 500 h aging under various conditions, including long-term air exposure, thermal, and humid treatment. This work opens up a new avenue of facile modified carbon electrodes for highly stable and hysteresis suppressed PSCs.

Hybrid PbS Quantum-Dot-in-Perovskite for High-Efficiency Perovskite Solar Cell.

In this study, a facile and effective approach to synthesize high-quality perovskite-quantum dots (QDs) hybrid film is demonstrated, which dramatically improves the photovoltaic performance of a perovskite solar cell (PSC). Adding PbS QDs into CH3 NH3 PbI3 (MAPbI3 ) precursor to form a QD-in-perovskite structure is found to be beneficial for the crystallization of perovskite, revealed by enlarged grain size, reduced fragmentized grains, enhanced characteristic peak intensity, and large percentage of (220) plane in X-ray diffraction patterns. The hybrid film also shows higher carrier mobility, as evidenced by Hall Effect measurement. By taking all these advantages, the PSC based on MAPbI3 -PbS hybrid film leads to an improvement in power conversion efficiency by 14% compared to that based on pure perovskite, primarily ascribed to higher current density and fill factor (FF). Ultimately, an efficiency reaching up to 18.6% and a FF of over ≈0.77 are achieved based on the PSC with hybrid film. Such a simple hybridizing technique opens up a promising method to improve the performance of PSCs, and has strong potential to be applied to prepare other hybrid composite materials.

Perovskite solar cells: must lead be replaced - and can it be done?

Perovskite solar cells have recently drawn significant attention for photovoltaic applications with a certified power conversion efficiency of more than 22%. Unfortunately, the toxicity of the dissolvable lead content in these materials presents a critical concern for future commercial development. This review outlines some criteria for the possible replacement of lead by less toxic elements, and highlights current research progress in the application of low-lead halide perovskites as optically active materials in solar cells. These criteria are discussed with the aim of developing a better understanding of the physio-chemical properties of perovskites and of realizing similar photovoltaic performance in perovskite materials either with or without lead. Some open questions and future development prospects are outlined for further advancing perovskite solar cells toward both low toxicity and high efficiency.

New insights into the origin of hysteresis behavior in perovskite solar cells.

Perovskite solar cells (PSCs) have received tremendous attention due to their stunning progress in photovoltaic performance. The hysteresis behavior, however, is one of the major concerning issues accompanying the development of PSCs. In this context, we propose a new mechanism that explains the origin of hysteresis behavior by analyzing the electrical processes after changing the external electrical bias: the compensating electric field to the scanning voltage induced by drifting carriers. This is further verified by experiments, where we observed much reduced hysteresis in the current density-voltage (J-V) characteristics for the PSCs based on a thinner perovskite layer, which is a result of more evenly distributed electrons and holes. Moreover, light illumination with different wavelengths was applied to vary the initial carrier distribution inside the perovskite layer. We found that J-V curves when illuminating the device with longer wavelengths exhibited diminished hysteresis, which could be a result of more evenly generated carriers due to a smaller absorptivity than that with short wavelength illumination. Based on the proposed model, three key factors affecting the hysteresis behavior were pointed out, including the initial carrier distribution, the carrier transport properties in the perovskite layer, and the carrier extraction properties at the interfaces. Strategies to construct hysteresis-free and stable PSCs have thus been accordingly proposed.