Surface wettability of various phases of titania thin films: Atomic-scale simulation studies.

In the paper, the wettability of different phases of TiO2 thin films (anatase, brookite, and rutile) have been studied using molecular-dynamics simulation. The principle of micro-wetting is discussed. The simulation results show that the contact angle decreases upon increasing the interaction energy between the water and the titanium dioxide interface during the wetting process. The values of contact angles from large to small are: rutile, brookite and anatase. The calculated equilibrium contact angles are 73.9°, 59.2°, and 43.7°, respectively. The reason is that the structural connection and the arrangement of the surface microtopography directly affect the movement of water droplets on the surface of the material, thus affecting the wettability. In addition, the amount of the interaction energy and the radial distribution function between these three interfaces and the droplets are calculated, and the density change of the droplet is analyzed further which indicate the difference in wetting between the three crystal structures. At the same time, by simulating and comparing the wettability of the trench surface and the original surface of anatase, it is inferred that the rough interface increases the contact angle with the droplet and reduces the wettability.

Difluorobenzylamine Treatment of Organolead Halide Perovskite Boosts the High Efficiency and Stability of Photovoltaic Cells.

As one of the most competitive light-harvesting materials, organometal halide perovskites have attracted great attention due to their low-cost and top-down solution fabricability. However, the instability of perovskites in a moist environment reduces the potential for their commercialization. In this study, novel 2,4-fluorobenzylamine (FBA) was employed as the passivation material, which could successfully suppress the defects and improve the moisture resistance of perovskites, resulting in an ultrahigh power conversion efficiency of 17.6% for the carbon-based perovskite solar cells with good stability. Meanwhile, the whole process of interactions between the H2O molecule and the perovskite lattice was first elucidated by density functional theory calculations, which demonstrated the underlying mechanism of the improvement of moisture stability with the FBA treatment. This work opens up a new route toward addressing the main obstacles in the practical application of perovskite devices under ambient conditions.

Validation of the Committed Action Questionnaire-8 and Its Mediating Role Between Experiential Avoidance and Life Satisfaction Among Chinese University Students.

Background: Committed action is one of the core processes of psychological flexibility derived from acceptance and commitment therapy. It has not been widely investigated in mainland China as appropriate measures are lacking. The current study aimed to validate a Chinese (Mandarin) version of the Committed Action Questionnaire (CAQ-8) in a non-clinical college sample and to explore whether committed action would have a mediating effect in the association between experiential avoidance (EA) and life satisfaction. Methods: We translated the CAQ-8 into Chinese (Mandarin). A total of 913 Chinese undergraduates completed a set of questionnaires measuring committed action, EA, mindful awareness, anxiety, depression, stress, and life satisfaction. For test-retest reliability, 167 respondents completed the CAQ-8 again 4 weeks later. Results: The entire scale of CAQ-8 (Mandarin) and two subscales showed adequate internal consistency and acceptable test-retest reliability. Confirmatory factor analyses confirmed the two-factor structure and the convergent and criterion validity were acceptable. Committed action was correlated with less EA, more mindful awareness, less depressive symptoms, less anxiety, less stress, and more life satisfaction. In bootstrap mediation analyses, committed action partially mediated the association between EA and life satisfaction. Conclusion: The results suggest that the CAQ-8 (Mandarin) is a brief, psychometrically sound instrument to investigate committed action in Chinese populations, and the relationship between EA and life satisfaction was partially explained by committed action. This study provides new information about the usefulness of CAQ-8 and supports the assumption that committed action may be considered a promising factors for improving life satisfaction who have involved in EA among an educated non-clinical population.

A Flexible and Stable Interpenetrated Indium Pyridylcarboxylate Framework with Breathing Behaviors and Highly Selective Adsorption of Cationic Dyes.

An interpenetrated indium pyridylcarboxylate framework, [NH2(CH3)2][In(L)2]·2.5DMF·5H2O (1), has been synthesized by employing a pyridylcarboxylate ligand, 4-(3-carboxylphenyl)picolinic acid (H2L), and an In3+ ion, with both chemical stability and framework flexibility. The desolvated 1 exhibits an uncommon breathing sorption behavior and shows highly selective adsorption for C2H2, C2H4, and CO2 over CH4. Furthermore, 1 shows rapid and higher adsorption efficiency for methylene blue and neutral red in aqueous solution.

Green Solution-Processed Tin-Based Perovskite Films for Lead-Free Planar Photovoltaic Devices.

The eco-friendly Sn-based perovskites have attracted more and more attention in lead-free perovskite photovoltaic field. However, the device performance and reproducibility are greatly challenged in preparing high-quality perovskite films. Here, we fabricated uniform and dense Sn-based perovskite films via a green gas pump treatment technology. Remarkably, we successfully fabricated a large-area (>20 cm2) Sn-based perovskite film with a mirror-like surface, which is the largest Sn-based perovskite film ever reported. Besides, we found that the phase separation phenomenon induced by excess SnF2 was eliminated when the pressure is 1500 Pa. Finally, we fabricated highly reproducible Sn-based solar cells and obtained an inspiring efficiency of 1.85%, which is the highest reported efficiency for Sn-based devices with a configuration of fluorine-doped tin oxide/compact TiO2/perovskite/hole transport material/electrode. Our results demonstrate the feasibility of using gas pump treatment technique to prepare high-quality Sn-based perovskite films, which paves a way for large-scale green manufacturing of Sn-based perovskite solar cells in the future.

Ultra-high open-circuit voltage of perovskite solar cells induced by nucleation thermodynamics on rough substrates.

To obtain high performance CH3NH3PbI3 perovskite solar cells, it is highly important to realise a high open-circuit voltage. Calculation results based on a modified diode model have indicated that a low bare ratio ϕ of the perovskite film is the most important factor determining the open-circuit voltage, where ϕ is defined as the ratio of the projection of the uncovered area of the perovskite film to the apparent area of the total substrate surface. To realise a low ϕ, we investigate the nucleation behaviour of crystals on rough substrates. The analysis results predict that, when CH3NH3PbI3 is deposited on conventional transparent conductive oxide substrates such as fluorine-doped tin oxide, preferential heterogeneous nucleation will occur on the concave regions of the substrate; then, depending on the subsequent growth step, full coverage of the perovskite film at both the macroscopic and microscopic scales is realised. As a result, an ultra-high open-circuit voltage, i.e., 1.20 V, can be achieved in devices using the full coverage CH3NH3PbI3 film. The thermodynamics theory of precipitation nucleation should shed light on solution engineering of thin films.