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Cations with suitable sizes to occupy an interstitial site of perovskite crystals have been widely used to inhibit ion migration and promote the performance and stability of perovskite optoelectronics. However, such interstitial doping inevitably leads to lattice microstrain that impairs the long-range ordering and stability of the crystals, causing a sacrificial trade-off. Here, we unravel the evident influence of the valence states of the interstitial cations on their efficacy to suppress the ion migration. Incorporation of a trivalent neodymium cation (Nd3+) effectively mitigates the ion migration in the perovskite lattice with a reduced dosage (0.08%) compared to a widely used monovalent cation dopant (Na+, 0.45%). The photovoltaic performances and operational stability of the prototypical perovskite solar cells are enhanced with a trace amount of Nd3+ doping while minimizing the sacrificial trade-off.

The feature endowing atomic Ni-N-C electrocatalysts with exceptional intrinsic alkaline hydrogen evolution activity is hitherto not well-documented and remains elusive. To this end, we rationally exploited the hierarchical porous carbon microstructures as scaffolds to construct unique Ni-N

Semi-transparent organic photovoltaics (OPVs) are an emerging solar-energy-harvesting technology with promising applications, such as rooftop energy supplies for environmentally friendly greenhouses. However, the poor operational stability of OPVs poses challenges to their feasibility as incessantly serving facilities. Here we report a reductive interlayer structure for semi-transparent OPVs that improves the operational stability of OPVs under continuous solar radiation. The interlayer effectively suppresses the generation of radicals from the electron transport layer under sunlight and prevents the structural decomposition of the organic photoactive layer during operation. The defects that serve as the charge carrier recombination sites are nullified by the electron-donating functional groups of the reduced molecules, which improves photovoltaic performance. The semi-transparent OPVs demonstrate a power conversion efficiency of 13.5% and an average visible transmittance of 21.5%, with remarkable operational stability (84.8% retention after 1,008 h) under continuous illumination. Greenhouse results show that the semi-transparent OPV roof benefits the survival rate and growth of the crops, indicating the importance of our approach in addressing food and energy challenges.

In this article, we develop a continuous periodic switching model depicting Wolbachia infection frequency dynamics in mosquito populations by releasing Wolbachia-infected mosquitoes, which is different from the discrete modeling efforts in the literature. We obtain sufficient conditions on the existence of a unique and exactly two periodic solutions and analyze the stability of each periodic solution, respectively. We also provide a brief discussion and several numerical examples to illustrate our theoretical results.

We describe highly efficient and stable bifacial perovskite solar cells incorporating carbon nanotube network films as a back contact enabling perovskite/CIS 4-terminal tandem solar cells to reach apower conversion efficiency of over 27%.

Precise control of the growth of 2D perovskites on 3D perovskites to form “trans-grain boundaries” 2D/3D structure for the preparation of flexible perovskite solar cells with a certified PCE up to 22.1% and excellent mechanical stability.

Glycolaldehyde, a C2 compound, is the simplest sugar molecule, but whether it inherently exists in plants remains unclear due to its complicated existence form in different reaction conditions.

Due to the lack of professional development time and awareness, well-directed training content, respect for teachers and value for education, the professional development of rural border elementary school teachers is a problem that needs to be solved urgently. The study suggests that the teaching faculty should be complemented and strengthened, the contents of teacher training should be “localized,” the internal drive of teachers should be stimulated, the respect for teachers and education should be promoted, thus improving the overall quality of the teaching faculty and promoting the balanced development of compulsory education.

In perovskite solar cells (PSCs), the hole-transport layer (HTL) plays an essential role in effective charge transport and extraction from the photoexcited perovskite, thus being significant for overall power conversion efficiency (PCE) and operational stability. So far, spiro-MeOTAD has been the most widely used HTL despite its inherent drawbacks, such as highly hygroscopic nature, poor conductivity, and mismatched energy-level alignment with the perovskite active layer. Here, a spiro-MeOTAD-based composite HTL modified by microwave method-synthesized carbon quantum dots (CQDs) was proposed and demonstrated as a promising HTL candidate for high-performance PSCs. The results demonstrated that the CQDs/spiro-MeOTAD composite HTL possesses several appealing characteristics for PSC applications, such as suitable energy levels for hole extraction, passivated interfacial trap states, and reduced recombination losses. Consequently, as compared to the control one using an unmodified spiro-MeOTAD HTL, (FAPbI

Summary Although great progress is being made toward improving the power conversion efficiency (PCE) and the operational stability of perovskite solar cells (PSCs), little attention is being paid to their mechanical reliability, which is particularly important for flexible PSCs (f-PCSs). Here, we have grown low-dimensional (LD) metal-halide perovskite (MHP) thin capping layer over the 3D MHP light-absorber thin film in f-PSCs in situ to improve their mechanical reliability. This resulted in f-PSCs with unprecedented, simultaneous improvements in PCE (21.0%), operational stability (T90, retention of 90% of the initial PCE, >800 h), and bending durability (T80 = 20,000 tension-only bending cycles). These synergistic virtuous effects are attributed to the LD MHP capping layer enhancing photocarriers extraction, providing protection against the environment, and “sealing” surface flaws on the 3D MHP thin film. The latter reduces the propensity for cracking in bending, which results in improved environmental stability and bending durability.

Precisely controlled synthesis is one of the key issues for single-atom catalysts (SACs) due to isolated atoms have high surface-free-energy toward aggregation. Here, we propose a facile cooperativ...

Carbon-supported single-atom catalysts (C-SACs) demonstrate great potential in various key electrochemical reactions. Nevertheless, the development of facile and economical strategies is highly appealing yet challenging given that the commonly used pyrolysis method has strict requirements on the structure and composition of precursors. Here, we demonstrate for the first time a facile and low-cost pyrolysis strategy assisted by molten salts at high temperature for preparing porous C-SACs with well-dispersed Co-N4 sites directly from a Chlorella precursor. Based on the X-ray absorption fine structure results and aberration-corrected scanning transmission electron microscopy images, we show that single atom Co-N4 moieties are anchored on a carbon matrix. A porous structure with a large specific surface area (2907 m2 g−1) and atomically dispersed active sites of Co provide the as-prepared Co-N/C-SAC with excellent electrocatalytic activity and stability for the ORR. The electrochemical measurements show that the half-wave potential and limited current density of this material are 0.83 V vs. RHE and 5.5 mA cm−2, respectively, which are comparable to those of commercial Pt/C.

Currently, pyrolysis as the most widely used method still has some key issues not well resolved for synthesis of carbon-supported single-atom catalysts (C-SACs), e.g., the sintering of metal atoms at high temperature as well as the high cost and complicated preparations of precursors. In this report, molten salts are demonstrated to be marvellous medium for preparation of C-SACs by pyrolysis of small molecular precursors (ionic liquid). The ultrastrong polarity on one hand establishes robust interaction with precursor and enables better carbonization, resulting in largely enhanced yield. On the other hand, the aggregation of metal atoms is effectively refrained while no nanoparticle or cluster is formed. By this strategy, a C-SAC with atomically dispersed Fe-N4 sites and a high specific area over 2000 m2 g−1 is obtained, which illustrates high ORR activity in both acid and alkaline media. Moreover, this SAC exhibits superior methanol tolerance and stability after acid soaking at 85 °C for 48 h. It is believed that the molten-salts-assisted pyrolysis can be developed into a routine strategy as it not only can largely simply the synthesis of C-SACs, but also can be extended to prepare other types of SACs.

The perovskite solar cell has emerged rapidly in the field of photovoltaics as it combines the merits of low cost, high efficiency, and excellent mechanical flexibility for versatile applications. However, there are significant concerns regarding its operational stability and mechanical robustness. Most of the previously reported approaches to address these concerns entail separate engineering of perovskite and charge-transporting layers. Herein we present a holistic design of perovskite and charge-transporting layers by synthesizing an interpenetrating perovskite/electron-transporting-layer interface. This interface is reaction-formed between a tin dioxide layer containing excess organic halide and a perovskite layer containing excess lead halide. Perovskite solar cells with such interfaces deliver efficiencies up to 22.2% and 20.1% for rigid and flexible versions, respectively. Long-term (1000 h) operational stability is demonstrated and the flexible devices show high endurance against mechanical-bending (2500 cycles) fatigue. Mechanistic insights into the relationship between the interpenetrating interface structure and performance enhancement are provided based on comprehensive, advanced, microscopic characterizations. This study highlights interface integrity as an important factor for designing efficient, operationally-stable, and mechanically-robust solar cells., Operational stability and mechanical robustness remain as engineering bottlenecks in perovskite solar cells technology. Here, Dong et al. introduce an interpenetrating perovskite at the electron-transporting-layer interface that enables a 1000-hour stable operation and high endurance against bending fatigue over 2500 cycles.

Due to their outstanding advantages like excellent moisture resistance and compatibility with up-scalable manufacturing processes, carbon (C) electrode hole transport layer (HTL)-free perovskite solar cells (PSCs) represent an excellent solution to the serious limitations caused by the commonly used HTL and expensive noble metal electrode. The C-electrode can be deposited using different techniques from various carbon allotropes and their derivatives. However, the choice of optimal carbon sources is still open to debate, which will certainly have a strong effect on the performance and long-term stability of the resulting PSCs. Here, the modular HTL-free C-PSCs were assembled by the lamination of two independently processed half-stacks of a semi-cell and a charge collector, where the C-electrodes were processed using a simple spray coating technique at low temperature (85 °C). Three typical carbon sources were used, i.e., multiwall carbon nanotube (MWCNT), carbon nanocoil (CNC), and graphene. A comparative study was conducted to determine the best candidate. Results indicated that MWCNT might be more preferable as the back electrode in HTL-free PSCs in terms of well-aligned band alignment, superior ability in extraction and collection of photo-generated holes. As a result, an improved power conversion efficiency (PCE) of 11.2% was achieved for modular MWCNT-based PSCs, and much improved thermal and humidity stabilities were also demonstrated. Our achievement demonstrates the irreplaceable role of tri-functional MWCNT in C-based HTL-free PSCs with integrated function: (i) back electrode; (ii) hole extraction and collection; and (iii) excellent moisture barrier.

Carbon-based single-atom catalysts (C-SACs), featured with flexible, well-defined atomic geometry and superior electrical conductivity, have experienced a rapid development in the last decade and proved unique opportunities in selective oxygen reduction reaction (ORR) electrocatalysis via direct 4e- pathway or alternative 2e- pathway for sustainable energy conversion and chemical synthesis. This concise review summarizes recent experimental efforts aiming at tailored selectivity, activities and derived progressive guidelines for catalyst design. First, the current exploration and development of synthetic methodologies of diverse C-SACs for ORR is briefly outlined. Then we present a key overview on structure-dependent catalytic selectivity and activity properties, in particular emphasizing on the microenvironment modulation of single-atom active sites from the aspects of regulating the central metal atoms, coordination environment and support properties. Besides, the dual active sites enabled synergistic catalysis for breaking conventional scaling relation are also highlighted. Finally, the current remaining challenges in C-SACs for ORR and related perspectives are proposed to shed some light on the further developments toward industrialization in the future.

Glycolaldehyde (HOCH2CHO, GA), the simplest molecule containing both hydroxyl and aldehyde groups, is structurally the most elementary member of monosaccharide sugars, which may provide new clues for probing the origin of life on planets like the Earth. Uncovering the existing state of GA in solution systems is an important scientific issue. Generally, methanol is used as the main mobile phase in the liquid chromatography analysis of GA, but the state of GA existing in methanol solution remains unknown, thus making it difficult to analyse GA accurately. Herein, the state and dynamic equilibrium of GA in methanol solution were systematically studied by UV-visible spectroscopy, nuclear magnetic resonance (1H-NMR) spectroscopy, liquid chromatography mass spectrometry (LC–MS) and density functional theory (DFT) calculations. The results demonstrated that the equilibrium component of GA in methanol solution is different from that in aqueous solution and that glycolaldehyde hemiacetal (GAHA) is a dominant component (>90%). Laying the foundation for experimental analysis, the transformation of different components at equilibrium was studied using DFT. The results confirm that hydrogen bonding-induced proton transfer occurs between the components at equilibrium. This work provides an important reference for the analysis of sugars and related compounds in various biochemical reactions.