Superhydrophobic Modification of Atomic Layer Deposition Antireflection Aluminum Oxide Film: A Simple Evaporative Coating Technique.

The antireflective transmittance-enhancing films have important applications in solar cells and other applications due to their self-cleaning and high light transmittance. However, obtaining high transmittance, highly durable, and superhydrophobic surfaces in a simple and easily accessible way is still a challenge. A simple evaporative coating technique has been proposed that can be used to prepare antireflective superhydrophobic aluminum oxide films using 1H,1H,2H,2H-perfluoroalkyltriethoxysilanes. The results show that the contact angle of grass-like alumina increased from 99.5° to 155°. The surface energy of grass-like alumina decreased from 17.96 to 1.93 mN/m. The maximum value of light transmittance is close to 98%, and the average transmittance is above 95%. The films have excellent ultraviolet resistance and thermal stability along with relative mechanical and chemical stability. Meanwhile, this method has an excellent capacity for shape preservation. The relationships between the evaporation temperature and time and the light transmittance and hydrophobic angle of the films were also investigated together. This approach has the potential to be extended to large-scale industrial production.

New intelligent multifunctional SiO2/VO2 composite films with enhanced infrared light regulation performance, solar modulation capability, and superhydrophobicity.

Highly transparent, energy-saving, and superhydrophobic nanostructured SiO2/VO2 composite films have been fabricated using a sol-gel method. These composite films are composed of an underlying infrared (IR)-regulating VO2 layer and a top protective layer that consists of SiO2 nanoparticles. Experimental results showed that the composite structure could enhance the IR light regulation performance, solar modulation capability, and hydrophobicity of the pristine VO2 layer. The transmittance of the composite films in visible region (Tlum) was higher than 60%, which was sufficient to meet the requirements of glass lighting. Compared with pristine VO2 films and tungsten-doped VO2 film, the near IR control capability of the composite films was enhanced by 13.9% and 22.1%, respectively, whereas their solar modulation capability was enhanced by 10.9% and 22.9%, respectively. The water contact angles of the SiO2/VO2 composite films were over 150°, indicating superhydrophobicity. The transparent superhydrophobic surface exhibited a high stability toward illumination as all the films retained their initial superhydrophobicity even after exposure to 365 nm light with an intensity of 160 mW . cm-2 for 10 h. In addition, the films possessed anti-oxidation and anti-acid properties. These characteristics are highly advantageous for intelligent windows or solar cell applications, given that they can provide surfaces with anti-fogging, rainproofing, and self-cleaning effects. Our technique offers a simple and low-cost solution to the development of stable and visible light transparent superhydrophobic surfaces for industrial applications.

An ab initio molecular dynamics investigation of the behaviour of amorphous substances in anodic aluminium oxide under electric field.

In order to elucidate the diffusion behaviour of ions in alumina during the anodic alumina process, the effects of electric field strength, hydration content, and electrolyte on amorphous alumina and hydrated alumina were studied using ab initio molecular dynamics. The results show that the diffusion rate of ions in alumina increases with the increase in electric field strength, but there is an extreme value. The maximum diffusion rate of Al ions in alumina monohydrate is 21.8 µm2/ms/V, while in alumina trihydrate, it is 16.7 µm2/ms/V. The ionic diffusion rate of hydrated alumina is one to two orders of magnitude larger than that of anhydrous amorphous alumina due to the effect of the drag of H ions, which reduces the migration activation energy. Electrolytes also affect the diffusion rate of alumina through the action of H ions. The increase in H ions will not only enhance the diffusion rate of hydrated alumina but also render the hydrous compound more vulnerable to breakdown.

An investigation using DFT into the impact of hydrogen on oxygen migration processes during aluminum anodization.

First-principles computations were utilized to examine the impact of H atoms on the surface behavior of O atoms on the (111) surface of Al and their infiltration behavior into the Al crystal, with the aim of elucidating the behavior of ions in the anodic process during aluminum oxidation. According to the findings, the "abstract" action of H atoms significantly lowers the energy barrier preventing O from entering the Al crystal. The addition of a H atom influences the diffusion of O atoms in the Al crystal as well, and this can lower the activation energy of O atom migration between the tetrahedral interstitial locations from 1.23 eV to 0.35 eV. We can benefit from knowing how ions are transported and anodic oxidation occurs.

Local Delivery of Glabridin by Biomolecular Microneedle to Accelerate Infected Wound Healing.

Applying antibacterial polymers and pro-regenerative small molecules are two individual strategies for accelerating wound healing. However, integrating those two unique approaches into one therapeutic platform that meets clinical requirements is still a challenge. Herein, a series of antibacterial gelatin methacrylate (GelMA)/ε-polylysine (ε-PL) composite hydrogels (termed as GP-n HGs, n = 0, 10, 20, and 30, respectively) are innovatively fabricated by ultraviolet light (UV) crosslinking. The GP-n HGs are proved to be broad-spectrum antibacterial and biocompatible. Among those GP-n HGs, the GP-20 HG is selectively processed into microneedle following a mold-casting method. Then, the glabridin is loaded into those needles to produce composite microneedle termed GP-20@Gla MN. An S. aureus-infected full-thickness defect model in rats is created to evaluate the wound-healing effect of GP-20@Gla MN. Furthermore, an RNA sequencing assay is performed to explore the possible molecular mechanisms of glabridin in promoting tissue regeneration, and many positive routes are summarized. This work is of significant novelty in fulfilling complex clinical needs by simultaneously optimizing the advanced microneedles' chemical compositions and physical structures. This work will provide a promising therapeutic platform for treating infected and chronic wounds.

Sustainable Recycling of Selenium-Based Optoelectronic Devices.

Selenium (Se), the world's oldest optoelectronic material, has been widely applied in various optoelectronic devices such as commercial X-ray flat-panel detectors and photovoltaics. However, despite the rare and widely-dispersed nature of Se element, a sustainable recycling of Se and other valuable materials from spent Se-based devices has not been developed so far. Here a sustainable strategy is reported that makes use of the significantly higher vapor pressure of volatile Se compared to other functional layers to recycle all of them from end-of-life Se-based devices through a closed-space evaporation process, utilizing Se photovoltaic devices as a case study. This strategy results in high recycling yields of ≈ 98% for Se and 100% for other functional materials including valuable gold electrodes and glass/FTO/TiO2 substrates. The refabricated photovoltaic devices based on these recycled materials achieve an efficiency of 12.33% under 1000-lux indoor illumination, comparable to devices fabricated using commercially sourced materials and surpassing the current indoor photovoltaic industry standard of amorphous silicon cells.

ß-Alanine-Anchored SnO2 Inducing Facet Orientation for High-Efficiency Perovskite Solar Cells.

SnO2 films as a promising electron transport layer (ETL) have been widely used in planar-type perovskite solar cells to achieve an impressive improvement in the conversion efficiency. However, compared with a mesoporous ETL, the interfacial charge carrier transfer of the SnO2 ETL is severely limited due to the issues of oxygen vacancy defects and crystal lattice mismatch between SnO2 and the perovskite, which generally leads to the growth of randomly stacked and porous perovskite layers and subsequently impacts the charge transport and transfer properties. In this work, we developed a facile approach by inducing a bifunctional molecule, ß-alanine, into the SnO2 ETL, which can serve as a bridge to modulate the interfacial charge transfer and the perovskite crystallization kinetics. Benefited by the interfacial ß-alanine, we grew a highly orientational perovskite layer that exhibited superior charge transport properties. Meanwhile, the ß-alanine caused an intimate connection between the perovskite and SnO2 to enhance the interfacial charge transfer. As a result, the power conversion efficiency (PCE) of the ß-alanine-modified device achieved a much-improved value of 19.67% and showed high reproducibility. This work provides a way for developing a high-performance ETL toward the scalable fabrication of highly efficient PSCs.

Novel Quasi-Solid-State Electrolytes based on Electrospun Poly(vinylidene fluoride) Fiber Membranes for Highly Efficient and Stable Dye-Sensitized Solar Cells.

To obtain new highly efficient and stable quasi-solid dye-sensitized solar cells (QS-DSSCs) that can meet the requirements for the large-scale commercial application of solar cells, we have developed a novel quasi-solid-state electrolyte, based on an electrospun polyvinylidene fluoride (PVDF) membrane. The structure and properties of electrospun PVDF membranes were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), thermogravimetric (TG), and mechanical testing. The results indicate that the electrospun PVDF membrane has a three-dimensional network structure with extremely high porosity, which not only acts as a barrier to prevent electrolyte leakage but also provides a channel for the transmission of ions in the electrolyte, thereby effectively guaranteeing the high photoelectric conversion efficiency of the cells. The membrane was observed to withstand the conditions of hot-press (110 °C), and exhibited good thermal stability and mechanical strength, which are critical for the long-term stability and safety of the cells. The photovoltaic characteristics and stabilities of QS-DSSCs were compared with DSSCs based on an ionic liquid electrolyte (L-DSSC). QS-DSSCs with an 80 µm thick nanofiber electrolyte membrane showed a conversion efficiency of 8.63%, whereas an identical cell based on the corresponding ionic liquid electrolyte showed an efficiency of 9.30%. The stability test showed that, under indoor and outdoor conditions, after 390 h, the L-DSSCs failed. Meanwhile, the QS-DSSCs also maintained 84% and 77% of the original efficiency. The results show that, compared to the liquid electrolyte, the design of the quasi-solid electrolytes based on electrospun PVDF nanofiber membrane not only demonstrates the high conversion efficiency of DSSCs but also enhances the stability of the DSSCs, which provides the possibility for the fabrication of solar cells with higher efficiency and stability.

Selection of an anti-solvent for efficient and stable cesium-containing triple cation planar perovskite solar cells.

The perovskite layer is a crucial component influencing high-performance perovskite solar cells (PSCs). In the one-step solution method, anti-solvents are important for obtaining smooth and uniform perovskite active layers. This work explored the effect of various anti-solvents on the preparation of triple cation perovskite active layers. In general, anti-solvents with low dielectric constants, low polarity, and low boiling point are suitable for the preparation of perovskite films. Microstructural and elemental analyses of the perovskite films were systematically conducted by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The photoelectric properties, carrier transfer, and recombination process in the PSCs were investigated using photocurrent-voltage characteristic curves and electrochemical impedance spectroscopy. Optimum performance was obtained when the anti-solvent was diethyl ether (DEE) and the ratio of the optimum amount of DEE to the volume of the precursor was 1 : 10. Meanwhile, we found that the partial replacement of formamidinium/methylammonium by cesium could increase the stability of the PSCs and enhance the power conversion efficiency from 15.49% to over 17.38%.

Synergic effects of upconversion nanoparticles NaYbF4:Ho3+ and ZrO2 enhanced the efficiency in hole-conductor-free perovskite solar cells.

Extending the spectral absorption of organic-inorganic mixed-cation perovskite solar cells (PSCs) from visible light to the near-infrared (NIR) range minimizes the nonabsorption loss of solar photons. Few studies have focused on the application of high-fluorescence NaYbF4:Ho3+ upconversion nanoparticles (UCNPs) in solar cells. In this study, NaYbF4:Ho3+ UCNPs were successfully prepared using a solvothermal method. We incorporated the NaYbF4:Ho3+ UCNPs into ZrO2 as the scaffold layer for FA0.4MA0.6PbI3 perovskite solar cells. This design enabled the dual-functional effects, that is, the harvesting of NIR light and its conversion to visible light and the reduction of the electron-hole recombination rate. The effect of different amounts of NaYbF4:Ho3+ UCNPs on the device performance was investigated in detail. The best-performance devices based on optimized addition of UCNPs (40 wt%) could achieve a power conversion efficiency as high as 14.32%, an increase of 28.8% compared with conventional ZrO2 nanoparticle-based PSCs (11.12%). The design of the synergetic operation of UCNPs and ZrO2 in the mesoporous structure of PSCs enhanced the photocurrent and photovoltage. The results offered the flexibility for the device architecture and broaden the solar spectral use of UCNP-based devices.

Application of mixed-organic-cation for high performance hole-conductor-free perovskite solar cells.

ABX3-type organic lead halide perovskites have gained increasing attention as light harvester for solar cells due to their high power conversion efficiency (PCE). Recently, it has become a trend to avoid the use of expensive hole-transport materials (HTMs) and precious metals, such as Au, to be competitive in future commercial development. In this study, we fabricated mixed-cation perovskite-based solar cells through one-step spin-coating using methylammonium (CH3NH3+) and formamidinium (HN=CHNH3+) cations to extend the optical absorption range into the red region and enhance the utilization of solar light. The synthesized hole-conductor-free cells with carbon electrode and mixed cations exhibited increased short-circuit current, outperforming the cells prepared with pure methylammonium, and PCE of 10.55%. This paper proposes an efficient approach for fabricating high-performance and low-cost perovskite solar cells.

Atomic Layer Deposition of TiO2 for a High-Efficiency Hole-Blocking Layer in Hole-Conductor-Free Perovskite Solar Cells Processed in Ambient Air.

In this study we design and construct high-efficiency, low-cost, highly stable, hole-conductor-free, solid-state perovskite solar cells, with TiO2 as the electron transport layer (ETL) and carbon as the hole collection layer, in ambient air. First, uniform, pinhole-free TiO2 films of various thicknesses were deposited on fluorine-doped tin oxide (FTO) electrodes by atomic layer deposition (ALD) technology. Based on these TiO2 films, a series of hole-conductor-free perovskite solar cells (PSCs) with carbon as the counter electrode were fabricated in ambient air, and the effect of thickness of TiO2 compact film on the device performance was investigated in detail. It was found that the performance of PSCs depends on the thickness of the compact layer due to the difference in surface roughness, transmittance, charge transport resistance, electron-hole recombination rate, and the charge lifetime. The best-performance devices based on optimized TiO2 compact film (by 2000 cycles ALD) can achieve power conversion efficiencies (PCEs) of as high as 7.82%. Furthermore, they can maintain over 96% of their initial PCE after 651 h (about 1 month) storage in ambient air, thus exhibiting excellent long-term stability.

A novel photoanode architecture of dye-sensitized solar cells based on TiO2 hollow sphere/nanorod array double-layer film.

A novel TiO(2) double-layer (DL) film consisting of TiO(2) hollow spheres (HSs) as overlayer and single-crystalline TiO(2) nanorod arrays (RAs) as underlayer was designed as the photoanode of dye-sensitized solar cells (DSSCs). This new-typed TiO(2) HS/RA DL film could significantly improve the efficiency of DSSCs owing to its synergic effects, i.e. the relatively large specific surface area of TiO(2) HSs for effective dye adsorption, enhanced light harvesting capability originated from TiO(2) RA film, and rapid interfacial electron transport in one-dimensional TiO(2) nanorod arrays. The overall energy-conversion efficiency of 4.57% was achieved by the formation of TiO(2) DL film, which is 16% higher than that formed by TiO(2) HS film and far larger than that formed by TiO(2) RA film (η=0.99%). The light absorption and interfacial electron transport, which play important roles in the efficiency of DSSCs, were investigated by UV-vis absorption spectra and electrochemical impedance spectra.