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Purpose Kelp is widely productive and inexpensive. The purpose of this study is to explore kelp liquid (KL) as an environment-friendly water-based lubricant, which is expected to replace some industrial lubricants and protect the environment while satisfying lubricating performance. Design/methodology/approach In this experiment, the soaked kelp was broken up by a wall-breaking machine to get the KL by a centrifuge. Elements and crystal structure of KL samples were characterized by X-ray photoelectron spectroscopy, X-ray diffraction and Raman spectra. The friction test is carried out by the relative movement of the polyethylene ball and the aluminum disk on the friction tester. Findings Friction experiments showed that 0.1 Wt.% KL has a good lubrication effect, and the average coefficient of friction is 0.063 under the condition of applying a 10 N load and moving at a speed of 2.0 cm/s. KL has good thermal conductivity with excellent cooling effect and high intermolecular force which makes high viscosity for excellent lubricating behavior, at the meantime molecules in solution remain stable which shows an excellent dispersibility. Originality/value At present, the research on kelp mainly focuses on its medicinal value and abundant nutritional value, and the research on its lubrication effect is less. Based on this situation, this paper explored the characteristics of KL as an environmentally friendly lubricant, which is expected to be used as a green cutting fluid.

Turnover of soil organic carbon (SOC) is strongly affected by a balance between mineral protection and microbial degradation. However, the mechanisms controlling the heterogeneous and preferential adsorption of different types of SOC remain elusive. In this work, the heterogeneous adsorption of humic substances (HSs) and microbial carbon (MC) on a clay mineral (nontronite NAu-2) during microbial-mediated Fe redox cycling was determined using time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results revealed that HSs pre-adsorbed on NAu-2 would partially inhibit structural modification of NAu-2 by microbial Fe(III) reduction, thus retarding the subsequent adsorption of MC. In contrast, NAu-2 without precoated HSs adsorbed a significant amount of MC from microbial polysaccharides as a result of Fe(III) reduction. This was attributed to the deposition of a thin Al-rich layer on the clay surface, which provided active sites for MC adsorption. This study provides direct and detailed molecular evidence for the first time to explain the preferential adsorption of MC over HSs on the surface of clay minerals in iron redox processes, which could be critical for the preservation of MC in soil. The results also indicate that ToF-SIMS is a unique tool for understanding complex organic-mineral-microbe interactions.

Determining the role of lattice oxygen in the oxygen evolution reaction (OER) is pivotal to understanding reaction mechanisms and predictive design of electrocatalysts based on transition metal oxi...

The understanding of ion solvation phenomena is of significance due to their influences on many important chemical, biological, and environmental processes. Mass spectrometry (MS)-based methods have been used to investigate this topic with molecular insights. As ion-solvent interactions are weak, ionization processes should be as soft as possible in order to retain solvation structures. An in situ liquid secondary ion MS (SIMS) approach developed in our group has been recently utilized in investigations of Li ion solvation in nonaqueous solution, and it detected a series of solvated Li ions. As traditionally SIMS has long been recognized as a hard ionization process with strong damage occurring at the sputtering interface, it is very interesting to study further how soft in situ liquid SIMS can be. In this work, we used halide ion hydration as an example to compare the ionization performance of the in situ liquid SIMS approach with regular electrospray ionization MS (ESI-MS). Results show that, although ESI has been recognized as a soft ionization method, nearly no solvated halide ions were detected by ESI-MS analysis, which acquired only strong signals of salt ion clusters. In contrast, in liquid SIMS spectra, a series of obvious hydrated halide ion compositions could be observed. We further evaluated the hydration numbers of halide ions and revealed the effects of the ion size, charge density, and polarizability on the hydration phenomenon. Our findings demonstrated that the in situ liquid SIMS approach is surprisingly soft, and it is expected to have very broad applications on investigation of various ion-solvent interactions and many other interesting chemical processes (e.g., the initial nucleation of nanoparticle formation) in liquid environment.

Epitaxial strain can cause both lattice distortion and oxygen nonstoichiometry, effects that are strongly coupled at heterojunctions of complex nickelate oxides. Here we decouple these structural a...

Perovskite solar cells (PSCs) have emerged as an attractive photovoltaic technology thanks to their outstanding power conversion efficiency (PCE). Further improvement in the device efficiency is limited by the recombination of the charge carriers in the perovskite layer even when employing heterojunction-based architectures. Here, we propose and demonstrate a p-type perovskite/n-type perovskite homojunction whose built-in electric field promotes oriented transport of the photo-induced carriers, thus reducing carrier recombination losses. By controlling the stoichiometry of the perovskite precursors, we are able to induce n-type or p-type doping. We integrate the homojunction structure in a planar PSC combining a thermally evaporated p-type perovskite layer on a solution-processed n-type perovskite layer. The PSC with a MAPbI3 homojunction achieves a PCE of 20.80% (20.5% certified PCE), whereas the PSC based on a FA0.15MA0.85PbI3 homojunction delivers a PCE of 21.38%. We demonstrate that the homojunction structure is an effective approach, beyond existing planar heterojunction PSCs, to achieve highly efficient PSCs with reduced carrier recombination losses. Carrier recombination limits the power conversion efficiency of perovskite solar cells. Here the authors construct a planar p–n homojunction perovskite solar cell to promote the oriented transport of carriers and reduce recombination, thus enabling power conversion efficiency of 21.3%.

Hybrid planar-Si/organic heterojunction solar cells have gained considerable interest in the fabrication of cost-effective and high-efficiency devices. However, most of high power conversion efficiency (PCE) performances have been obtained with particular structures, front surface texture or rear surface field layer. In this paper, we provide a simple method without complex structures, and demonstrate the superiority and the mechanism of using stannic oxide (SnO2) as an insertion layer. The SnO2 insertion layer takes the place of the Schottky barrier, which reduces barrier height of rear Si to enhance charge transfer. And the effect of the insertion layer reduces contact resistance and enhances contact quality of rear Si side. Meanwhile, it has been indicated that the Si-O-Sn bonds were formed by SnO2 and Si dangling bond (Si-), which have a passivation effect on the Si surface to effectively suppress the recombination losses. Furthermore, simulations using density functional theory (DFT) confirm that the electrostatic potential can improve electronic transmission from Si to Sn between Si-O-Sn bonds. Finally, for the hybrid planar-Si/PEDOT:PSS heterojunction solar cells without any special structures, the highest PCE of 14.1% was achieved, up 10.8% compared with that without SnO2 insertion layer. These findings provide an effective way of improving Si/metal contact via a simple, room temperature process for other photovoltaic devices.

In p-type multicrystalline silicon solar cells, defects in silicon bulk are well known to act as carrier recombination centers and considerably affect the conversion efficiency of cells. In this study, effective minority carrier lifetime (τeff) mapping and deep-level transient spectroscopy (DLTS) data were utilized to evaluate gettering efficiency and hydrogenation passivation in bulk defects. Microwave photoconductivity decay method was used to illustrate the effect of phosphorus gettering behavior and hydrogenation process on the bulk carrier lifetime of multicrystalline silicon. Results showed that τeff drastically improved after gettering and further increased after hydrogenation. DLTS results further revealed six traps corresponding to interstitial iron (Fei), Fe–O complex, FeB complex, vanadium, Fei complex and divacancy oxygen. The main trap in a nongettered sample was related to Fei, with two deep levels at about EV + 0.373 and EV + 0.470 eV. However, the Fei complex was the main trap in the gettered sample, with two deep traps at about EV+0.390 and EV+0.442 eV. Finally, we concluded that Fei defect and FeB complex can be significantly removed by phosphorus diffusion gettering. Moreover, divacancy-oxygen complexes, vanadium and Fe–O defects were effectively passivated by hydrogenation process. Fei complex, however, was hardly removed by these two process.

Instability of the perovskite materials, especially in high humidity, is one of the major limitations that hinders the development of perovskite devices. Herein, to eliminate the degradation of perovskite solar cells in humid air, a water-resistant perovskite absorption layer is proposed by introducing a macrocycle-type cyclodextrin material (β-CD) into the films. The β-CD was proved to be capable of facilitating the crystallization of grains and enhancing the stability of the perovskite by forming supramolecular interactions with organic cations through the hydrogen bonding in the perovskite films. Consequently, the average efficiency of the PSCs remarkably increased from 16.19% to 19.98%. The champion solar cell even delivered an efficiency of 20.09%. The PSCs with β-CD exhibited superior long-term stability in ambient air without encapsulation, which retained 90% of the initial efficiency after continuous AM 1.5 illumination in ambient air with 80% humidity for 300 h.

Earth-abundant nickel-containing perovskite oxides (ANiO3) are highly active materials for the oxygen evolution reaction (OER). The strong nickel-oxygen (Ni–O) covalency, tunable by A-site chemical substitution, contributes to both bulk and surface material properties like the formation of oxygen vacancies (v •• O ) and OER activity. Here we quantify the coverage of OER relevant adsorbates on a series of La1−x Sr x NiO3−δ (LSNO, 0 ⩽ x ⩽ 0.5) epitaxial thin films exposed to humid environments by ambient pressure x-ray photoelectron spectroscopy. While all LSNO film compositions investigated here have comparable hydroxide coverages at the relative humidities (RHs) probed (1.5 × 10−5 – 0.2%RH), the amount of under-coordinated surface oxygen increases notably with Sr content. We interpret differences in the free energy of adsorption (ΔG ads,i ) of these OER intermediates, inferred from adsorption isotherms, in the context of proposed v •• O -mediated OER mechanisms, consistent with the pH-dependent OER activity observed here for LSNO. We find that Sr incorporation enhances the affinity of LSNO surfaces for these under-coordinated oxygen species, in line with calculations in the literature.

The perovskite oxide LaNiO3 is a promising oxygen electrocatalyst for renewable energy storage and conversion technologies. Here, it is shown that strontium substitution for lanthanum in coherently strained, epitaxial LaNiO3 films (La1− xSrxNiO3) significantly enhances the oxygen evolution reaction (OER) activity, resulting in performance at x = 0.5 comparable to the state‐of‐the‐art catalyst Ba0.5Sr0.5Co0.8Fe0.2O3− δ. By combining X‐ray photoemission and X‐ray absorption spectroscopies with density functional theory, it is shown that an upward energy shift of the O 2p band relative to the Fermi level occurs with increasing x in La1− xSrxNiO3. This alloying step strengthens Ni 3d–O 2p hybridization and decreases the charge transfer energy, which in turn accounts for the enhanced OER activity.

A novel ferroelectric coupling photovoltaic effect is reported to enhance the open‐circuit voltage (VOC) and the efficiency of CH3NH3PbI3 perovskite solar cells. A theoretical analysis demonstrates that this ferroelectric coupling effect can effectively promote charge extraction as well as suppress combination loss for an increased minority carrier lifetime. In this study, a ferroelectric polymer P(VDF‐TrFE) is introduced to the absorber layer in solar cells with a proper cocrystalline process. Piezoresponse force microscopy (PFM) is used to confirm that the P(VDF‐TrFE):CH3NH3PbI3 mixed thin films possess ferroelectricity, while the pure CH3NH3PbI3 films have no obvious PFM response. Additionally, with the applied external bias voltages on the ferroelectric films, the devices begin to show tunable photovoltaic performance, as expected for the polarization in the poling process. Furthermore, it is shown that through the ferroelectric coupled effect, the efficiency of the CH3NH3PbI3‐based perovskite photovoltaic devices is enhanced by about 30%, from 13.4% to 17.3%. And the open‐circuit voltages (VOC) reach 1.17 from 1.08 V, which is reported to be among the highest VOCs for CH3NH3PbI3‐based devices. It should be noted in particular that the thickness of the layer is less than 160 nm, which can be regarded as semi‐transparent.

Migration of ions can lead to photoinduced phase separation, degradation, and current-voltage hysteresis in perovskite solar cells (PSCs), and has become a serious drawback for the organic-inorganic hybrid perovskite materials (OIPs). Here, the inhibition of ion migration is realized by the supramolecular cation-π interaction between aromatic rubrene and organic cations in OIPs. The energy of the cation-π interaction between rubrene and perovskite is found to be as strong as 1.5 eV, which is enough to immobilize the organic cations in OIPs; this will thus will lead to the obvious reduction of defects in perovskite films and outstanding stability in devices. By employing the cation-immobilized OIPs to fabricate perovskite solar cells (PSCs), a champion efficiency of 20.86% and certified efficiency of 20.80% with negligible hysteresis are acquired. In addition, the long-term stability of cation-immobilized PSCs is improved definitely (98% of the initial efficiency after 720 h operation), which is assigned to the inhibition of ionic diffusions in cation-immobilized OIPs. This cation-π interaction between cations and the supramolecular π system enhances the stability and the performance of PSCs efficiently and would be a potential universal approach to get the more stable perovskite devices.

In order to obtain a good passivation of a silicon surface, more and more stack passivation schemes have been used in high-efficiency silicon solar cell fabrication. In this work, we prepared a-Si:H(i)/Al2O3 stacks on KOH solution-polished n-type solar grade mono-silicon(100) wafers. For the Al2O3 film deposition, both thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) were used. Interface trap density spectra were obtained for Si passivation with a-Si films and a-Si:H(i)/Al2O3 stacks by a non-contact corona C-V technique. After the fabrication of a-Si:H(i)/Al2O3 stacks, the minimum interface trap density was reduced from original 3 × 1012 to 1 × 1012 cm−2 eV−1, the surface total charge density increased by nearly one order of magnitude for PE-ALD samples and about 0.4 × 1012 cm−2 for a T-ALD sample, and the carrier lifetimes increased by a factor of three (from about 10 μs to about 30 μs). Combining these results with an X-ray photoelectron spectroscopy analysis, we discussed the influence of an oxidation precursor for ALD Al2O3 deposition on Al2O3 single layers and a-Si:H(i)/Al2O3 stack surface passivation from field-effect passivation and chemical passivation perspectives. In addition, the influence of the stack fabrication process on the a-Si film structure was also discussed in this study.

We demonstrate a simple and fast post-deposition treatment with high process compatibility on the hole transport material (HTM) Spiro-MeOTAD in vapor-assisted solution processed methylammonium lead triiodide (CH3NH3PbI3)-based solar cells. The prepared Co-doped p-type Spiro-MeOTAD films are treated by O3 at room temperature for 5 min, 10 min, and 20 min, respectively, prior to the deposition of the metal electrodes. Compared with the traditional oxidation of Spiro-MeOTAD films overnight in dry air, our fast O3 treatment of HTM at room temperature only needs just 10 min, and a relative 40.3% increment in the power conversion efficiency is observed with respect to the result of without-treated perovskite solar cells. This improvement of efficiency is mainly attributed to the obvious increase of the fill factor and short-circuit current density, despite a slight decrease in the open-circuit voltage. Ultraviolet photoelectron spectroscopy (UPS) and Hall effect measurement method are employed in our study to determine the changes of properties after O3 treatment in HTM. It is found that after the HTM is exposed to O3, its p-type doping level is enhanced. The enhancement of conductivity and Hall mobility of the film, resulting from the improvement in p-doping level of HTM, leads to better performances of perovskite solar cells. Best power conversion efficiencies (PCEs) of 13.05% and 16.39% are achieved with most properly optimized HTM via CH3NH3I vapor-assisted method and traditional single-step method respectively.

Plasma-enhanced atom layer deposition (PEALD) can deposit denser films than those prepared by thermal ALD. But the improvement on thickness uniformity and the decrease of defect density of the films deposited by PEALD need further research. A PEALD process from trimethyl-aluminum (TMA) and oxygen plasma was investigated to study the influence of the conditions with different plasma powers and deposition temperatures on uniformity and growth rate. The thickness and refractive index of films were measured by ellipsometry, and the passivation effect of alumina on n-type silicon before and after annealing was measured by microwave photoconductivity decay method. Also, the effects of deposition temperature and annealing temperature on effective minority carrier lifetime were investigated. Capacitance-voltage and conductance-voltage measurements were used to investigate the interface defect density of state (D it) of Al2O3/Si. Finally, Al diffusion P+ emitter on n-type silicon was passivated by PEALD Al2O3 films. The conclusion is that the condition of lower substrate temperature accelerates the growth of films and that the condition of lower plasma power controls the films’ uniformity. The annealing temperature is higher for samples prepared at lower substrate temperature in order to get the better surface passivation effects. Heavier doping concentration of Al increased passivation quality after annealing by the effective minority carrier lifetime up to 100 μs.