聚合物层状组装膜

介绍了近几年来我们研究组在层状组装膜的构筑以及功能化研究方面取得的一些最新进展.包括结合表面溶胶-凝胶技术与静电层状组装技术,实现了二阶非线性基团在层状组装多层膜中的非对称排列,制备了具有二阶非线性效应的膜材料;采用室温压印技术,发展了一种简便、经济和具有普适性的层状组装聚合物膜图案化方法;以轻度交联的聚合物微凝胶为构筑基元,制备了具有高负载量的聚合物层状组装膜;发展了一种基于离子剥离技术的层状组装自支持膜制备方法;基于层状组装技术,制备了具有超疏水和抗反射功能的涂层.     

Dynamic sequential layer-by-layer deposition method for fast and region-selective multilayer thin film fabrication

We present a newly devised technique, the dynamic layer-by-layer (LbL) deposition method, that is designed to take advantage of the LbL deposition method and fluidic devices. Polyelectrolyte solutions are sequentially injected through the fluidic LbL deposition device to quickly build well-defined multilayer films on a selected region with a linear increase in the material deposited. Multilayer film fabrication by this new method on a specific region was proven to be fast and effective. The effects on film quality of the processing parameters such as concentration of polyelectrolytes, flow rate, and contact time were investigated. A half-tethered self-standing film on a substrate was fabricated to demonstrate the effectiveness and the region-selective deposition capability of the devised dynamic LbL deposition method.     

Bio-inspired multi-scale structures in dye-sensitized solar cell

Dye-sensitized solar cells (DSSCs) provide a technique and economic alternative concept to present p–n junction photovoltaic devices. For a DSSC, light is absorbed by a sensitizer, which is anchored to the surface of a wide band semiconductor. Charge separation takes place at the interface via photo-induced electron injection from the dye into the conduction band of the semiconductor. Nanocrystalline oxide semiconductor photo-anode films play an important role in photo-electrical conversion efficiency of DSSCs. In this review, we summarize the recent advances of multi-scale structures of DSSCs in the view of bio-inspired materials and analyze the influence factors of a variety of multi-scale structures on photo-electrical conversion in DSSCs, which will provide a strategy for structure design on the novel solar cell.     

空气下光诱导有机金属卤化钙钛矿薄膜的降解机理

近几年来钙钛矿材料作为新兴光伏材料取得了巨大的发展进步,但有机无机杂化钙钛矿较差的环境稳定性限制了它的大规模应用。因此深入研究钙钛矿材料的降解机制有助于开发更稳定的钙钛矿光伏器件。本文基于透射电子显微学的微观形貌观察、晶体结构及元素成分表征,详细研究了杂化钙钛矿CH_3NH_3PbI_3薄膜在光照以及空气共同作用下的降解机理。研究发现,光诱导下CH_3NH_3PbI_3薄膜会与空气中的氧气发生交互作用,同时生成六方晶态PbI_2甚至氧化为非晶态化合物PbI_(2-2x)O_x (0.4 x 0.6),而其衰减位点主要存在于薄膜与空气接触的表面。降解过程中,由于存在着挥发性分解产物(I_2,CH_3NH_2)的大量丢失,薄膜的表面会产生许多小孔洞,继而形成一种蜂窝状的介孔衰竭通道。而这种衰竭方式主要与光照下钙钛矿中光生电子与氧气结合形成超氧根自由基(O_2~(·-))有关,该基团诱导了CH_3NH_3PbI_3向PbI_2和非晶氧化态的转变。本文揭示了空气中光照诱导钙钛矿薄膜的降解机理,这将为未来设计和优化更稳定的钙钛矿太阳能电池提供全面的实验数据与理论支持。     

Bifunctional electroactive nanostructured membranes

The advent of techniques based upon the spontaneous assembly of different materials with control over molecular architecture has afforded the fabrication of composite thin films for many nanotechnological applications. The layer-by-layer technique (LbL), in particular, has largely been used in the molecular level processing of nanohybrid systems in the form of multilayers, owing to its low cost and experimental simplicity. In this study we describe the fabrication of a novel, bifunctional film containing platinum nanoparticles/polyamidoamine (PAMAM) dendrimers. Pt nanoparticles were chemically synthesized/stabilized in the presence of PAMAM dendrimers and incorporated in LbL films in conjunction with nickel tetrasulfonated phthalocyanine (NiTsPc). A metallophthalocyanine was chosen because of its well-defined redox activity. Indium tin oxide (ITO)-covered glass plates were used as substrates for film deposition. The nanocomposites displayed high electrocatalytic activity toward dopamine and hydrogen peroxide molecules, two compounds with dissimilar chemical properties.     

8.01% CuInGaSe2 solar cells fabricated by air-stable low-cost inks

CuInGaSe(2) (CIGS), a promising thin film solar cell material, has gained lots of attention in decades due to its high energy conversion efficiency and potential lower manufacture cost over conventional Si solar cells. As a cheaper processing method compared to vacuum-based techniques, solution-based deposition has been successfully applied to fabricate electronic devices, such as transistors and solar cells. In this paper, we reported CIGS thin film solar cells with an energy conversion efficiency reaching up to 8.01% using air-stable, low-cost inks. The newly developed inks consist of commercially available, low-cost compounds and solvents and can be processed using a variety of printing and coating techniques. More importantly, the inks can produce CIGS films free of copper selenides and amorphous carbon, two common by-products from solution-based CIGS processes. The mechanism for the transformation from metal salt precursor films to CIGS absorber thin films and the influence of selenium vapour pressure on absorber film quality and photovoltaic device performance were investigated and discussed. High-quality CIGS films with micrometer-sized crystals were obtained by using higher selenization partial pressure.     

Layer-by-layer assembled multilayer TiO(x) for efficient electron acceptor in polymer hybrid solar cells

We demonstrate that TiO(x) nanocomposite films fabricated using electrostatic layer-by-layer (LbL) assembly improve the power conversion efficiency of photovoltaic cells compared to conventional TiO(x) films fabricated via the sol-gel process. For this study, titanium precursor/poly(allylamine hydrochloride) (PAH) multilayer films were first deposited onto indium tin oxide-coated glass to produce TiO(x) nanocomposites (TiO(x)NC). The specific effect of the LbL processed TiO(x) on photovoltaic performance was investigated using the planar bilayer TiO(x)NC and highly regioregular poly(3-hexylthiophene) (P3HT) solar cells, and the P3HT/LbL TiO(x)NC solar cells showed a dramatic increase in power efficiency, particularly in terms of the short current density and fill factor. The improved efficiency of this device is mainly due to the difference in the chemical composition of the LbL TiO(x)NC films, including the much higher Ti(3+)/Ti(4+) ratio and the highly reactive facets of crystals as demonstrated by XPS and XRD measurement, thus enhancing the electron transfer between electron donors and acceptors. In addition, the grazing incidence wide-angle X-ray scattering (GIWAXS) study revealed the presence of more highly oriented P3HT stacks parallel to the substrate on the LbL TiO(x)NC film compared to those on the sol-gel TiO(x) films, possibly influencing the hole mobility of P3HT and the energy transfer near and at the interface between the P3HT and TiO(x) layers. The results of this study demonstrate that this approach is a promising one for the design of hybrid solar cells with improved efficiency.     

表面印迹交替层状组装薄膜

在简要概述非常规交替层状组装这一进展后,重点总结了如何利用非常规交替层状组装以实现表面印迹膜的制备.模板分子与聚电解质在溶液中组装形成超分子复合物,然后以此超分子复合物为构筑基元,与感光性高分子,如重氮树脂,通过常规交替层状组装形成聚合物多层膜.利用聚合物多层膜之间的光化学反应形成稳定的多层膜,然后去除模板分子得到分子...     

Layer-by-layer assembly as a versatile bottom-up nanofabrication technique for exploratory research and realistic application

The layer-by-layer (LbL) adsorption technique offers an easy and inexpensive process for multilayer formation and allows a variety of materials to be incorporated within the film structures. Therefore, the LbL assembly method can be regarded as a versatile bottom-up nanofabrication technique. Research fields concerned with LbL assembly have developed rapidly but some important physicochemical aspects remain uninvestigated. In this review, we will introduce several examples from physicochemical investigations regarding the basics of this method to advanced research aimed at practical applications. These are selected mostly from recent reports and should stimulate many physical chemists and chemical physicists in the further development of LbL assembly. In order to further understand the mechanism of the LbL assembly process, theoretical work, including thermodynamics calculations, has been conducted. Additionally, the use of molecular dynamics simulation has been proposed. Recently, many kinds of physicochemical molecular interactions, including hydrogen bonding, charge transfer interactions, and stereo-complex formation, have been used. The combination of the LbL method with other fabrication techniques such as spin-coating, spraying, and photolithography has also been extensively researched. These improvements have enabled preparation of LbL films composed of various materials contained in well-designed nanostructures. The resulting structures can be used to investigate basic physicochemical phenomena where relative distances between interacting groups is of great importance. Similarly, LbL structures prepared by such advanced techniques are used widely for development of functional systems for physical applications from photovoltaic devices and field effect transistors to biochemical applications including nano-sized reactors and drug delivery systems.     

Graphene/inorganic nanocomposites: Evolving photocatalysts for solar energy conversion for environmental remediation

Current energy crisis and environmental issues, including depletion of fossil fuels, rapid industrialization, and undesired CO₂ emission resulting in global warming has created havoc for the global population and significantly affected the quality of life. In this scenario the environmental problems in the forefront of research priorities. Development of renewable energy resources particularly the efficient conversion of solar light to sustainable energy is crucial in addressing environmental problems. In this regard, the synthesis of semiconductors-based photocatalysts has emerged as an effective tool for different photocatalytic applications and environmental remediation. Among different photocatalyst options available, graphene and graphene derivatives such as, graphene oxide (GO), highly reduced graphene oxide (HRG), and doped graphene (N, S, P, B-HRG) have become rising stars on the horizon of semiconductors-based photocatalytic applications. Graphene is a single layer of graphite consisting of a unique planar structure, high conductivity, greater electron mobility, and significantly very high specific surface area. Besides, the recent advancements in synthetic approaches have led to the cost-effective production of graphene-based materials on a large-scale. Therefore, graphene-based materials have gained considerable recognition for the production of semiconducting photocatalysts involving other semiconducting materials. The graphene-based semiconductors photocatalysts surpasses electron-holes pairs recombination rate and lowers the energy band gap by tailoring the valence band (VB) and conduction band (CB) leading to the enhanced photocatalytic performance of hybrid photocatalysts. Herein, we have summarized the latest developments in designing and fabrication of graphene-based semiconducting photocatalysts using a variety of commonly applied methods such as, post-deposition methods, in-situ binding methods, hydrothermal and/or solvothermal approaches. In addition, we will discuss the photocatalytic properties of the resulting graphene-based hybrid materials for various environmental remediation processes such as; (i) clean H₂ fuel production, photocatalytic (ii) pollutants degradation, (iii) photo-redox organic transformation and (iv) photo-induced CO₂ reduction. On the whole, by the inclusion of more than 300 references, this review possibly covered in detail the aspects of graphene-based semiconductor photocatalysts for environmental remediation processes. Finally, the review will conclude a short summary and discussion about future perspectives, challenges and new directions in these emerging areas of research.     

Self-assembled graphene/azo polyelectrolyte multilayer film and its application in electrochemical energy storage device

Graphene/azo polyelectrolyte multilayer films were fabricated through electrostatic layer-by-layer (LbL) self-assembly, and their performance as electrochemical capacitor electrode was investigated. Cationic azo polyelectrolyte (QP4VP-co-PCN) was synthesized through radical polymerization, postpolymerization azo coupling reaction, and quaternization. Negatively charged graphene nanosheets were prepared by a chemically modified method. The LbL films were obtained by alternately dipping a piece of the pretreated substrates in the QP4VP-co-PCN and nanosheet solutions. The processes were repeated until the films with required numbers of bilayers were obtained. The self-assembly and multilayer surface morphology were characterized by UV-vis spectroscopy, AFM, SEM, and TEM. The performance of the LbL films as electrochemical capacitor electrode was estimated using cyclic voltammetry. Results show that the graphene nanosheets are densely packed in the multilayers and form random graphene network. The azo polyelectrolyte cohesively interacts with the nanosheets in the multilayer structure, which prevents agglomeration of graphene nanosheets. The sheet resistance of the LbL films decreases with the increase of the layer numbers and reaches the stationary value of 1.0 × 10(6) Ω/square for the film with 15 bilayers. At a scanning rate of 50 mV/s, the LbL film with 9 bilayers shows a gravimetric specific capacitance of 49 F/g in 1.0 M Na(2)SO(4) solution. The LbL films developed in this work could be a promising type of the electrode materials for electric energy storage devices.     

Supersonic molecular beam growth of thin films of organic materials: A novel approach to controlling the structure,morphology, and functional properties

Thin films of semiconducting molecular materials can be grown with a seeded supersonic molecular beam epitaxy (SuMBE), which provides unprecedented control over structural, morphological, and, therefore, functional properties. This novel technique of deposition takes full advantage of its ability to regulate the initial state of the molecular precursors in the beams and, in particular, the kinetic energy, to control the morphology, structure, and functional properties of growing films. This article reviews the state of the art of SuMBE, discussing the basic aspects of the technique and the major achievements so far. The major results obtained with respect to growth on dielectrics and metal substrates of films of oligothiophenes and pentacene and with respect to the codeposition of phthalocyanines and fullerenes are discussed and compared with the state of the art of more conventional organic molecular beam deposition. The potential impact of SuMBE in the field of π‐conjugated materials and devices is also examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2501–2521, 2003     

A Fast Deposition‐Crystallization Procedure for Highly Efficient Lead Iodide Perovskite Thin‐Film Solar Cells

Thin‐film photovoltaics based on alkylammonium lead iodide perovskite light absorbers have recently emerged as a promising low‐cost solar energy harvesting technology. To date, the perovskite layer in these efficient solar cells has generally been fabricated by either vapor deposition or a two‐step sequential deposition process. We report that flat, uniform thin films of this material can be deposited by a one‐step, solvent‐induced, fast crystallization method involving spin‐coating of a DMF solution of CH₃NH₃PbI₃ followed immediately by exposure to chlorobenzene to induce crystallization. Analysis of the devices and films revealed that the perovskite films consist of large crystalline grains with sizes up to microns. Planar heterojunction solar cells constructed with these solution‐processed thin films yielded an average power conversion efficiency of 13.9±0.7 % and a steady state efficiency of 13 % under standard AM 1.5 conditions.     

Impedance change induced by varying polymerization temperature of conducting polymer thin films

In this study, we use a conducting polymer precursor to build layer-by-layer (LbL) films. Thermal conversion of the polymer precursor to conducting polymer makes the LbL films intractable, so the LbL films can be used as protective layers in salt solution. The conducting polymer LbL film shows stabilizing effect on top of another LbL thin film that contains nanoparticles. The LbL film prepared in this study shows a 35-fold increase of conductivity than the literature values obtained from non-conducting polymer films. The stabilization of the films is the result of the polymerization of the conducting polymer, so other anionic polymers or nanoparticles may be used to afford additional functionalities.     

Improved efficiency of photovoltaics based on CdSe nanorods and poly(3-hexylthiophene) nanofibers

We present photovoltaic devices based on a blend of the conjugated polymer poly(3-hexylthiophene) (P3HT) with cadmium selenide nanorods, where the solvent for film deposition has been carefully chosen to optimize the film morphology. Using 1,2,4-trichlorobenzene (TCB), which has a high boiling point, as solvent for P3HT it is possible to obtain a fibrilar morphology, providing extended pathways for hole transport. Blend devices fabricated using this solvent gave solar power conversion efficiencies of 2.6%. This indicates that efficient transport of electrons and holes is achieved in these films, allowing them to operate effectively at solar illumination intensities.     

Pulsed Laser Deposition as a Tool for the Development of All Solid-State Microbatteries

All-solid-state lithium ion batteries (LIB) are currently the most promising technology for next generation electrochemical energy storage. Many efforts have been devoted in the past years to improve performance and safety of these devices. Nevertheless, issues regarding chemical and mechanical stability of the different components still hinder substantial improvements. Pulsed laser deposition (PLD) has proved to be an outstanding technique for the deposition of thin films of materials of interest for the fabrication of LIB. Thanks to its versatility and possible fine tuning of the thin film properties, PLD promises to be a very powerful tool for the fabrication of model systems which would allow to study in detail material properties and mechanisms contributing to LIB degradation. Nevertheless, PLD presents difficulties in the deposition of LIB components, mainly due to the presence of elements with large difference of atomic mass in their chemical composition. In this review, we report the main challenges and solution strategies used for the deposition through PLD of complex oxides thin films for LIB.     

光诱导钌配合物的几何异构和结构异构反应研究进展

金属钌(Ru)的配合物具有丰富的基态和激发态的光物理、光化学性质,在太阳能转换、光催化以及分子识别等方面都得到了广泛深入的研究.光诱导的钌配合物的异构反应是其颇具特色的一类光反应,研究光异构反应对于光能量转化、信息储存以及"分子光开关"和"分子马达"的设计具有重要的意义.本文小结和综述了钌配合物的光诱导几何异构和结构异构反应的特性和机理以及最新的研究进展.     

Sol-Gel Processed TiO2 Films for Photovoltaic Applications

The dye sensitized solar cells (DYSC) provides a technically and economically credible alternative concept to present day p-n junction photovoltaic devices. In contrast to the conventional systems where the semiconductor assumes both the task of light absorption and charge carrier transport the two functions are separated here. Light is absorbed by a sensitizer which is anchored to the surface of a wide band gap semiconductor. Charge separation takes place at the interface via photo-induced electron injection from the dye into the conduction band of the solid. Carriers are transported in the conduction band of the semiconductor to the charge collector. The present concepts evolved in the context of research on mesoporous oxide semiconductor films prepared via a sol-gel process. The use of transition metal complexes having a broad absorption band in conjunction with oxide films of nanocrstalline morphology permits to harvest a large fraction of sunlight. Nearly quantitative conversion of incident photons into electric current is achieved over a large spectral range extending over the whole visible region. Overall solar (standard AM 1.5) to electric conversion efficiencies over 10% have been reached. There are good prospects to produce these cells at lower cost than conventional devices. The lecture will present the current state of the field. We shall discuss new concepts of the dye-sensitized nanocrystalline solar cell (DYSC) including solid heterojunction variants and analyze the perspectives for the future development of the technology into the next millennium.     

高效率变色WO3多聚体/1，10-DAD自组装薄膜的制备

A novel high-efficient photochromic self-assembly multilayered film has been fabricated from WO3 and 1,10-DAD solution using molecular deposition technique.The dependence of photochromic behavior on with WO3 in the WO3-polymer/1,10-DAD self-assembly film was discussed in comparison with WO3/4,4-BAMBp system.The results clearly show that organic molecules determine the charge density of the photo-induced charge-tracsfer complexes,andthus manipu-late the structure and the photochromic properties of the films.     

Ternary single‐source precursors for polycrystalline thin‐film solar cells

The development of thin‐film solar cells on flexible, lightweight, space‐qualified substrates provides an attractive cost solution for fabricating solar arrays with high specific power (W kg^?1). The use of a polycrystalline chalcopyrite absorber layer for thin‐film solar cells is considered as the next generation in photovoltaic devices. At NASA GRC we have focused on the development of new single‐source precursors (SSPs) and their utility to deposit the chalcopyrite semiconducting layer (CIS) onto flexible substrates for solar‐cell fabrication. The syntheses and thermal modulation of SSPs via molecular engineering are described. Thin‐film fabrication studies demonstrate that the SSPs can be used in a spray chemical vapor deposition process for depositing CIS at reduced temperatures, and result in electrical properties that are suitable for photovoltaic devices. Copyright © 2002 John Wiley & Sons, Ltd.