Showing papers on "Coating published in 2020"

Scalable fabrication and coating methods for perovskite solar cells and solar modules

Abstract: Since the report in 2012 of a solid-state perovskite solar cell (PSC) with a power-conversion efficiency (PCE) of 9.7% and a stability of 500 h, intensive efforts have been made to increase the certified PCE, reaching 25.2% in 2019. The PCE of PSCs now exceeds that of conventional thin-film solar-cell technologies, and the rate at which this increase has been achieved is unprecedented in the history of photovoltaics. Moreover, the development of moisture-stable and heat-stable materials has increased the stability of PSCs. Small-area devices ( 100 cm2) substrates required for commercialization. Thus, materials and methods need to be developed for coating large-area PSCs. In this Review, we discuss solution-based and vapour-phase coating methods for the fabrication of large-area perovskite films, examine the progress in performance and the parameters affecting the properties of large-area coatings, and provide an overview of the methodologies for achieving high-efficiency perovskite solar modules. The scalable fabrication of perovskite solar cells and solar modules requires the development of new materials and coating methods. In this Review, we discuss solution-based and vapour-phase coating methods for large-area perovskite films and examine the progress in performance and the parameters affecting large-area coatings.

Understanding of perovskite crystal growth and film formation in scalable deposition processes

Abstract: Hybrid organic-inorganic perovskite photovoltaics (PSCs) have attracted significant attention during the past decade. Despite the stellar rise of laboratory-scale PSC devices, which have reached a certified efficiency over 25% to date, there is still a large efficiency gap when transiting from small-area devices to large-area solar modules. Efficiency losses would inevitably arise from the great challenges of homogeneous coating of large-area high quality perovskite films. To address this problem, we provide an in-depth understanding of the perovskite nucleation and crystal growth kinetics, including the LaMer and Ostwald ripening models, which advises us that fast nucleation and slow crystallization are essential factors in forming high-quality perovskite films. Based on these cognitions, a variety of thin film engineering approaches will be introduced, including the anti-solvent, gas-assisted and solvent annealing treatments, Lewis acid-base adduct incorporation, etc., which are able to regulate the nucleation and crystallization steps. Upscaling the photovoltaic devices is the following step. We summarize the currently developed scalable deposition technologies, including spray coating, slot-die coating, doctor blading, inkjet printing and vapour-assisted deposition. These are more appealing approaches for scalable fabrication of perovskite films than the spin coating method, in terms of lower material/solution waste, more homogeneous thin film coating over a large area, and better morphological control of the film. The working principles of these techniques will be provided, which direct us that the physical properties of the precursor solutions and surface characteristics/temperature of the substrate are both dominating factors influencing the film morphology. Optimization of the perovskite crystallization and film formation process will be subsequently summarized from these aspects. Additionally, we also highlight the significance of perovskite stability, as it is the last puzzle to realize the practical applications of PSCs. Recent efforts towards improving the stability of PSC devices to environmental factors are discussed in this part. In general, this review, comprising the mechanistic analysis of perovskite film formation, thin film engineering, scalable deposition technologies and device stability, provides a comprehensive overview of the current challenges and opportunities in the field of PSCs, aiming to promote the future development of cost-effective up-scale fabrication of highly efficient and ultra-stable PSCs for practical applications.

Black phosphorus composites with engineered interfaces for high-rate high-capacity lithium storage.

Abstract: High-rate lithium (Li) ion batteries that can be charged in minutes and store enough energy for a 350-mile driving range are highly desired for all-electric vehicles. A high charging rate usually leads to sacrifices in capacity and cycling stability. We report use of black phosphorus (BP) as the active anode for high-rate, high-capacity Li storage. The formation of covalent bonds with graphitic carbon restrains edge reconstruction in layered BP particles to ensure open edges for fast Li+ entry; the coating of the covalently bonded BP-graphite particles with electrolyte-swollen polyaniline yields a stable solid-electrolyte interphase and inhibits the continuous growth of poorly conducting Li fluorides and carbonates to ensure efficient Li+ transport. The resultant composite anode demonstrates an excellent combination of capacity, rate, and cycling endurance.

Highly stable Zn metal anodes enabled by atomic layer deposited Al 2 O 3 coating for aqueous zinc-ion batteries

Abstract: Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted increasing attention as an energy storage technology for large-scale applications, due to their high capacity (820 mA h g−1 and 5854 A h L−1), inherently high safety, and their low cost. However, the overall performance of ZIBs has been seriously hindered by the poor rechargeability of Zn anodes, because of the dendrite growth, passivation, and hydrogen evolution problems associated with Zn anodes. Herein, Al2O3 coating by an atomic layer deposition (ALD) technique was developed to address the aforementioned problems and improve the rechargeability of Zn anodes for ZIBs. By coating the Zn plate with an ultrathin Al2O3 layer, the wettability of Zn was improved and corrosion was inhibited. As a result, the formation of Zn dendrites was effectively suppressed, with a significantly improved lifetime in the Zn–Zn symmetric cells. With the optimized coating thickness of 100 cycles, 100Al2O3@Zn symmetric cells showed a reduced overpotential (36.5 mV) and a prolonged life span (over 500 h) at 1 mA cm−2. In addition, the 100Al2O3@Zn has been verified in Zn–MnO2 batteries using layered δ-MnO2 as the cathode and consequently exhibits superior electrochemical performance with a high capacity retention of 89.4% after over 1000 cycles at a current density of 1 mA cm−2 (3.33C for MnO2) was demonstrated. It is expected that the novel design of Al2O3 modified Zn anodes may pave the way towards high-performance aqueous ZIBs and shed light on the development of other metal anode-based battery systems.

MXene Printing and Patterned Coating for Device Applications

Abstract: As a thriving member of the 2D nanomaterials family, MXenes, i.e., transition metal carbides, nitrides, and carbonitrides, exhibit outstanding electrochemical, electronic, optical, and mechanical properties. They have been exploited in many applications including energy storage, electronics, optoelectronics, biomedicine, sensors, and catalysis. Compared to other 2D materials, MXenes possess a unique set of properties such as high metallic conductivity, excellent dispersion quality, negative surface charge, and hydrophilicity, making them particularly suitable as inks for printing applications. Printing and pre/post-patterned coating methods represent a whole range of simple, economically efficient, versatile, and eco-friendly manufacturing techniques for devices based on MXenes. Moreover, printing can allow for complex 3D architectures and multifunctionality that are highly required in various applications. By means of printing and patterned coating, the performance and application range of MXenes can be dramatically increased through careful patterning in three dimensions; thus, printing/coating is not only a device fabrication tool but also an enabling tool for new applications as well as for industrialization.

Flexible MXene/Silver Nanowire-Based Transparent Conductive Film with Electromagnetic Interference Shielding and Electro-Photo-Thermal Performance.

Abstract: Transparent conductive film (TCF) is promising for optoelectronic instrument applications. However, designing a robust, stable, and flexible TCF that can shield electromagnetic waves and work in harsh conditions remains a challenge. Herein, a multifunctional and flexible TCF with effective electromagnetic interference shielding (EMI) performance and outstanding electro-photo-thermal effect is proposed by orderly coating Ti3C2Tx MXene and a silver nanowire (AgNW) hybrid conductive network using a simple and scalable solution-processed method. Typically, the air-plasma-treated polycarbonate (PC) film was sequentially spray-coated with MXene and AgNW to construct a highly conductive network, which was transferred and partly embedded into an ultrathin poly(vinyl alcohol) (PVA) film using spin coating coupled with hot pressing to enhance the interfacial adhesion. The peeled MXene/AgNW-PVA TCF exhibits an optimal optical and electrical performance of sheet resistance 18.3 Ω/sq and transmittance 52.3%. As a consequence, the TCF reveals an effective EMI shielding efficiency of 32 dB in X-band with strong interfacial adhesion and satisfactory flexibility. Moreover, the high electrical conductivity and localized surface plasmon resonance (LSPR) effect of hybrid conductive network endow the TCF with low-voltage-driven Joule heating performance and excellent photothermal effect, respectively, which can ensure the normal functioning under extreme cold condition. In view of the comprehensive performance, this work offers new solutions for next-generation transparent EMI shielding challenges.

A “PDMS-in-water” emulsion enables mechanochemically robust superhydrophobic surfaces with self-healing nature

Abstract: It is highly challenging to construct a durable superhydrophobic coating for practical applications since the coating is easily destroyed by mechano-chemical attack. To address this issue, a “PDMS-in-water” emulsion approach is for the first time adopted to design a mechanochemically robust superhydrophobic cotton fabric with intelligent self-healing nature, without using any fluorine-containing components. With this approach, PDMS molecules firstly penetrate into the cotton fiber, and then graft onto the surface of the cotton fabric with a strong binding force, creating hierarchical rough structures and lowering the surface energy simultaneously. Benefitting from this design, the PDMS@cotton fabric exhibits high superhydrophobicity with a water contact angle over 155°, surpassing all the PDMS-in-organic solvent based approaches. Impressively, the surface repairs its superhydrophobicity throughout the whole lifetime though damaged by machine washing or abrasion (>100 cycles), due to the self-diffusion process of PDMS molecules from the inner part to the outer surface of the cotton fibers to minimize surface free energy. Besides, the superhydrophobic coatings display superior chemical stability in strongly acidic and alkaline solution, and maintain similar textile physical properties of the cotton fabric, such as elongation at break, tensile strength, etc. Our environment-friendly “PDMS-in-water” approach can be easily integrated into industrial textile finishing treatment and is promising to apply to various substrates with robust superhydrophobic surfaces.

Superhydrophobic ZIF-8-Based Dual-Layer Coating for Enhanced Corrosion Protection of Mg Alloy.

Abstract: Magnesium (Mg) and its alloys are regarded as the most promising engineering materials because of their unique property. However, the Mg alloys were easily corroded in humid environments, which restricted their wider applications. Herein, the superhydrophobic ZIF-8/PVDF/LDH (SZPL) double-layered coating was fabricated on Mg alloys via electrodeposition and dip-coating methods, which consisted of the underlying layered double hydroxide (LDH) transition structure and top superhydrophobic zeolitic imidazolate framework-8 (ZIF-8) layer. Besides, the LDH transition structure not only worked as a protection shield but also strengthened the binding force between the substrate and the top superhydrophobic ZIF-8 layer. The top superhydrophobic ZIF-8 layer could serve as an armor on the LDH layer to further prevent the corrosive ions from infiltrating the microporous defects. In addition, the as-prepared SZPL double-layered coating showed robust superhydrophobic and self-cleaning properties, which could block the electrolyte invasion. Furthermore, the electrochemical tests demonstrated that the SZPL coating highly enhanced the corrosion protection ability of Mg alloys. Moreover, the superhydrophobic ZIF-8-based coating could still retain excellent anticorrosion property after immersion in 3.5 wt % NaCl solution for 7 days. The enhanced anticorrosion ability was ascribed to the fact that a synergistic effect of the underlying LDH transition layer hindered the transmission of aggressive ions and the top superhydrophobic ZIF-8-based coating decreased the contact area of the substrate with corrosive solution. Therefore, such coatings offer a new strategy for fabricating excellent anticorrosive coatings with robust superhydrophobicity and self-cleaning performance on metal substrates.

A Surface Coating that Rapidly Inactivates SARS-CoV-2.

Abstract: SARS-CoV-2, the virus that causes the disease COVID-19, remains viable on solids for periods of up to 1 week, so one potential route for human infection is via exposure to an infectious dose from a solid. We have fabricated and tested a coating that is designed to reduce the longevity of SARS-CoV-2 on solids. The coating consists of cuprous oxide (Cu2O) particles bound with polyurethane. After 1 h on coated glass or stainless steel, the viral titer was reduced by about 99.9% on average compared to the uncoated sample. An advantage of a polyurethane-based coating is that polyurethane is already used to coat a large number of everyday objects. Our coating adheres well to glass and stainless steel as well as everyday items that people may fear to touch during a pandemic, such as a doorknob, a pen, and a credit card keypad button. The coating performs well in the cross-hatch durability test and remains intact and active after 13 days of being immersed in water or after exposure to multiple cycles of exposure to the virus and disinfection.

Pursuit of reversible Zn electrochemistry: a time-honored challenge towards low-cost and green energy storage

Abstract: The world’s mounting demands for environmentally benign and efficient resource utilization have spurred investigations into intrinsically green and safe energy storage systems. As one of the most promising types of batteries, the Zn battery family, with a long research history in the human electrochemical power supply, has been revived and reevaluated in recent years. Although Zn anodes still lack mature and reliable solutions to support the satisfactory cyclability required for the current versatile applications, many new concepts with optimized Zn/Zn2+ redox processes have inspired new hopes for rechargeable Zn batteries. In this review, we present a critical overview of the latest advances that could have a pivotal role in addressing the bottlenecks (e.g., nonuniform deposition, parasitic side reactions) encountered with Zn anodes, especially at the electrolyte-electrode interface. The focus is on research activities towards electrolyte modulation, artificial interphase engineering, and electrode structure design. Moreover, challenges and perspectives of rechargeable Zn batteries for further development in electrochemical energy storage applications are discussed. The reviewed surface/interface issues also provide lessons for the research of other multivalent battery chemistries with low-efficiency plating and stripping of the metal. Using novel functional electrolytes to stabilize zinc batteries could help power technology including wearable electronics without the costs and hazards of lithium-ion devices. Jingwen Zhao and Guanglei Cui from the Chinese Academy of Sciences in Qingdao review how the performance of zinc batteries, which have high energy storage but unsatisfactory cyclability, can be improved through modified electrolytes that limit unwanted (electro)chemical processes. Especially, a shift from water-based electrolytes towards polymers can tremendously extend zinc battery lifetimes, while simultaneously enabling packaging into devices. Other approaches include coating electrodes with polymers or inorganic materials to encourage uniform zinc deposition during recharging. Electrodes that combine zinc with carbon fibers, or form the metal into 3D sponges, can also ensure reliable recharging. Zn battery family with a long research history in the human electrochemical power supply has been revived and reevaluated in recent years. However, Zn anode in rechargeable batteries still lacks mature and reliable solutions to support the satisfactory cyclability required for the current versatile applications. In this paper, novel functional electrolytes, modified electrode-electrolyte interfaces and advanced electrode structures for addressing the bottlenecks encountered in rechargeable Zn anodes are reviewed, highlighting the mechanisms and open questions in practical applications.

Dielectric Polarization in Inverse Spinel-Structured Mg2TiO4 Coating to Suppress Oxygen Evolution of Li-Rich Cathode Materials

Abstract: High-energy Li-rich layered cathode materials (≈900 Wh kg-1 ) suffer from severe capacity and voltage decay during cycling, which is associated with layered-to-spinel phase transition and oxygen redox reaction. Current efforts mainly focus on surface modification to suppress this unwanted structural transformation. However, the true challenge probably originates from the continuous oxygen release upon charging. Here, the usage of dielectric polarization in surface coating to suppress the oxygen evolution of Li-rich material is reported, using Mg2 TiO4 as a proof-of-concept material. The creation of a reverse electric field in surface layers effectively restrains the outward migration of bulk oxygen anions. Meanwhile, high oxygen-affinity elements of Mg and Ti well stabilize the surface oxygen of Li-rich material via enhancing the energy barrier for oxygen release reaction, verified by density functional theory simulation. Benefited from these, the modified Li-rich electrode exhibits an impressive cyclability with a high capacity retention of ≈81% even after 700 cycles at 2 C (≈0.5 A g-1 ), far superior to ≈44% of the unmodified counterpart. In addition, Mg2 TiO4 coating greatly mitigates the voltage decay of Li-rich material with the degradation rate reduced by ≈65%. This work proposes new insights into manipulating surface chemistry of electrode materials to control oxygen activity for high-energy-density rechargeable batteries.