Comparison of ZnO:Al,ITO and carbon nanotube transparent conductive layers in flexible solar cells applications

In the paper the mechanical, optical and electrical parameters of transparent conductive layers (TCLs) made of carbon nanotubes and metal conductive oxides are explored and compared. All investigated materials are deposited on transparent, flexible polymer foils used for solar cell applications. Obtained results are compared with available parameters of rigid transparent conductive oxides (TCOs) as well as literature reports about Indium–Tin Oxide (ITO) on flexible substrates. Presented paper is a report from the preliminary stage of a new flexible solar cell construction.     

Transparente leitfähige Elektroden

Transparent conductive oxides and alternative transparent electrodes for organic photovoltaics and OLEDs Organic, photoactive devices, such as OLEDs or organic solar cells, currently use indium tin oxide (ITO) as transparent electrode. Whereas ITO is industry‐proven for many years and shows very good electrical and optical properties, its application for lowcost and flexible devices might not be optimal. For such applications innovative technologies such as networkbased metal nanowire or carbon nanotube electrodes, graphene, conductive polymers, metal thin‐films and alternative transparent conductive oxides emerge. Although some of these technologies are rather experimental and far from application, some of them have the potential to replace ITO in selected applications.     

Transparent Plasmonic Nanowire Electrodes via Self‐Organised Ion Beam Nanopatterning

A self‐organised approach for the synthesis of transparent metal nanowire arrays is based on defocused ion beam sputtering. The nanowire arrays, supported on low‐cost dielectric substrates (glass slides), feature a dual functionality: they exhibit anisotropic conductivity, with sheet resistances which are reduced in comparison to those of transparent conductive oxides, and additionally they support localised plasmon resonances. The latter represents an attractive feature in view of plasmon enhanced photon harvesting applications, in which the nanostructured metal electrodes are employed as an alternative to conventional transparent conductive oxides.     

Development of new transparent conductors and device applications utilizing a multidisciplinary approach

Transparent and conductive films are key components for optoelectronic devices. They are applied as n-type transparent electrical contacts for inorganic and organic light emitting diodes, solar cells and flat panel displays as well as p- and n-type active semiconductive oxides to setup wide band gap p-n junctions and devices for the emerging field of transparent and radiation hard electronics.The demand for these films is strongly increasing due to the extensive market growth in these areas but the solutions available today only partially fulfill the requirements on low resistivity, high transmittance, large area deposition, low cost manufacturing, and ability for fine patterning, light scattering and precise alignment of the electronic structure to surrounding semiconductors.The cooperation of five Fraunhofer Institutes within the “Fraunhofer Project MAVO METCO” aims towards establishing fundamental knowledge and control about the defect chemistry, structure and morphology of the transparent semiconductive oxides. The goal is to achieve materials with outstanding properties such as n-type transparent conductive oxides with tailored work function and excellent durability, novel delafossite based p-type materials allowing cost effective large area deposition, oxide based p-n heterojunctions and Ag based electrodes to be used for thin film photovoltaics and organic light emitting diodes.Starting from first-principle modelling of the electronic structure, we address the development of new transparent conductive layers by PVD and Sol-Gel ending up with device implementation for OLEDs and organic as well as Si based a-Si:H/µc-Si:H and HIT solar cells.     

Wide-gap layered oxychalcogenide semiconductors: Materials, electronic structures and optoelectronic properties

Applying the concept of materials design for transparent conductive oxides to layered oxychalcogenides, several p-type and n-type layered oxychalcogenides were proposed as wide-gap semiconductors and their basic optical and electrical properties were examined. The layered oxychalcogenides are composed of ionic oxide layers and covalent chalcogenide layers, which bring wide-gap and conductive properties to these materials, respectively. The electronic structures of the materials were examined by normal/inverse photoemission spectroscopy and energy band calculations. The results of the examinations suggested that these materials possess unique features more than simple wide-gap semiconductors. Namely, the layered oxychalcogenides are considered to be extremely thin quantum wells composed of the oxide and chalcogenide layers or 2D chalcogenide crystals/molecules embedded in an oxide matrix. Observation of step-like absorption edges, large band gap energy and large exciton binding energy demonstrated these features originating from 2D density of states and quantum size effects in these layered materials.     

氧化物热电材料研究进展

氧化物基热电材料具有高温稳定性、抗氧化性和安全长效等优点而受到人们的广泛关注, 但其应用受到了热电性能的限制。本文详细介绍了几种典型氧化物热电体系, 如层状钴基氧化物、钙钛矿结构化合物、透明导电氧化物和一些新型氧化物热电材料的研究进展。从能带结构和微观形貌两方面入手进行调节, 以达到热电材料热学性能和电学性能的协调统一。分析了氧化物热电材料研究中的主要问题, 并对未来的发展提出了一些新的思路。     

Niobium oxides and niobates physical properties: Review and prospects

For the last 75 years several studies have been reporting on the physical properties of niobium oxides, but there is still many contradictory, inconsistent and insufficient information on these metal oxides. This review will begin by describing the niobium oxygen system and the different stoichiometric and non-stoichiometric phases, specifically Nb, NbO, NbO₂, Nb₂O₅ and Nb₂O_5−δ. The crystalline phases and polymorphs of these materials are often inconsistently identified in different works and thus, a clarification of the nomenclature of the several niobium oxides polymorph and their crystalline structure is also presented. Due to their interesting physical properties, many applications of these materials have been suggested such as solid electrolytic capacitors, catalysis, photochromic devices, transparent conductive oxides or memristors, becoming obvious that a good understanding of niobium oxides physical properties and their control is essential and urgent. Additionally, a short review on different types of niobates, namely alkali niobates, columbite niobates and rare earth niobates and the relation of the properties of these materials with niobium oxides will be presented.     

TCO/metal/TCO structures for energy and flexible electronics

There is increasing attention paid to improving transparent conductive electrodes for applications in large area photovoltaic devices and displays that are being developed for energy and electronics. To date, transparent and conductive oxides (TCO) based on In₂O₃, ZnO, or SnO₂ are commonly used, but advanced devices require new electrodes with lower resistivities than previously achieved and with optical properties superior to those of the present generation. TCO/metal/TCO multilayer structures have emerged as an interesting alternative because they provide optical and electrical characteristics globally superior to those attainable with a single-layer TCO or metal electrode and can be deposited at low temperatures onto inexpensive plastic substrates. Indeed, the fabrication of thin film devices on flexible substrates has substantial interest for application to lightweight products and implementation of roll-to-roll deposition processes that can significantly reduce production costs. In this sense, organic electronics that require low deposition temperatures have the best chance to be the first transferred from conventional glass to inexpensive plastic substrates. The present critical review summarizes current TCO/metal/TCO research results, first analyzed for materials and thickness selection as a function of the optical transmittance and electrical resistance parameters, and then analyzed according to other important properties such as mechanical reliability and thermal and humidity stability. The review concludes with a brief discussion of the results obtained for TCO/metal/TCO structures applied as electrodes in several organic electronic devices.     

高分子材料导电性能改善研究进展

提高高分子材料导电性能的方法,主要有掺杂、与其它材料复合、改变导电高分子的结构等方式。掺杂能够改变高分子材料中已有电子能带的能级,使得高分子中能带间的能量差减小,载流子迁移的阻力随之减小。与其它材料复合多为材料能提供载流子迁移的通道、与导电高分子材料形成大的共轭体系、改善链与链之间的有序性或增加复合物的紧密度,从而提高复合材料的导电性,与导电高分子复合的材料多为金属或金属氧化物、无机非金属纳米材料以及一些普通的有机高分子。改变导电高分子的结构能改善聚合物的规整度,提高其结晶度。导电高分子材料具有广泛的应用前景,今后需要在提高导电高分子电导率的同时改善其溶解性、加工性以及稳定性等综合性能,以实现导电高分子的实用化。     

Printable Transparent Conductive Films for Flexible Electronics

Printed electronics are an important enabling technology for the development of low‐cost, large‐area, and flexible optoelectronic devices. Transparent conductive films (TCFs) made from solution‐processable transparent conductive materials, such as metal nanoparticles/nanowires, carbon nanotubes, graphene, and conductive polymers, can simultaneously exhibit high mechanical flexibility, low cost, and better photoelectric properties compared to the commonly used sputtered indium‐tin‐oxide‐based TCFs, and are thus receiving great attention. This Review summarizes recent advances of large‐area flexible TCFs enabled by several roll‐to‐roll‐compatible printed techniques including inkjet printing, screen printing, offset printing, and gravure printing using the emerging transparent conductive materials. The preparation of TCFs including ink formulation, substrate treatment, patterning, and postprocessing, and their potential applications in solar cells, organic light‐emitting diodes, and touch panels are discussed in detail. The rational combination of a variety of printed techniques with emerging transparent conductive materials is believed to extend the opportunities for the development of printed electronics within the realm of flexible electronics and beyond.     

Eigenschaften amorpher transparenter leitfähiger Oxide (a‐TCOs)

Properties of amorphous transparent conducting oxides (a‐TCOs) In this contribution the optical and electrical properties of amorphous transparent conductive oxides (a‐TCOs) are analysed by means of atomistic material modelling. The investigation of model structures by computer simulations allows a deeper understanding of the physical phenomena. In the case of the a‐TCOs deep energy levels in the electronic band structure, that reduce for example the optical transparency, can be linked to structural defects on the atomic scale. This allows a well‐directed search for strategies which anneal these defects.     

锂离子电池锡基负极材料研究进展

综述了锂离子电池锡基负极材料的研究进展,锡基钢极材料可分为氧化物,复合氧化物,合金三类,其储锂机理都为合金机理,对氧化物的丰重于电极反应的详细过程,对复合氧化物的研究重点则是储锂机理,而锡合金则是最有希望进入商业化市场的锡基钢极材料,其中锡与锂可逆形成合金,另一不与锂反应的金属作为导电基体与框架,容纳合金以改善循环性能。     

Low temperature deposition of indium tin oxide films by plasma ion-assisted evaporation

Coatings of transparent conductive oxides, especially indium tin oxide (ITO), are important in different fields. So far, application of these materials has been limited to substrates with high thermal stability. We describe an improved coating process for ITO based on plasma ion-assisted evaporation at a substrate temperature below 100 degrees C, which is suitable for organic substrates. In characterizing the thin films, we used the classical Drude theory to calculate the resistivity from optical film properties and compared the data with linear four-point measurements. X-ray diffraction spectroscopy was used to determine the structural properties of the thin films.     

Optical and magnetic properties of transition metal oxides

The extremely strong coupling of conduction electrons with local spins in transition metal oxides leads to many intriguing electronic and optical properties, which are currently of great interest. Among these intriguing properties, the discovery of colossal magnetoresistance in manganese oxides has sparked a number of studies on the magnetic and electronic properties of these materials as well as the exploration of the relevant new materials phase.     

碳纳米管在超级电容器中的应用研究进展

超级电容器是近年来发展起来的一种新型储能装置。碳纳米管由于具有独特的中空结构，良好的导电性和高的比表面积，被认为是超级电容器理想的电极材料之一，引起了广泛的关注。通过介绍碳纳米管在超级电容器中的应用研究进展，评述了碳纳米管、活化碳纳米管、碳纳米管／金属氧化物复合物以及碳纳米管／导电聚合物复合物用做超级电容器电极材料的特点和性能。认为单纯的碳纳米管由于比表面积小，比容量偏低。化学活化可以显著提高碳纳米管的比表面积，增大其比电容。将碳纳米管与准电容材料金属氧化物或导电聚合物复合。可以发挥各自的优势，从而得到低成本、高性能的复合电极材料，将是今后发展的一个方向。     

ZnO layers grown by Atomic Layer Deposition: A new material for transparent conductive oxide

We demonstrate possibility of a control (by selection of zinc precursors and variation of a growth temperature) of electrical properties of ZnO films grown by Atomic Layer Deposition (ALD). ZnO films grown by ALD are used in test photovoltaic devices (solar cells) as transparent conductive oxides for upper, transparent layer in inorganic and organic solar cells, and as n-type partners of p-type CdTe.     

Highly Deformable and See‐Through Polymer Light‐Emitting Diodes with All‐Conducting‐Polymer Electrodes

Despite the high expectation of deformable and see‐through displays for future ubiquitous society, current light‐emitting diodes (LEDs) fail to meet the desired mechanical and optical properties, mainly because of the fragile transparent conducting oxides and opaque metal electrodes. Here, by introducing a highly conductive nanofibrillated conducting polymer (CP) as both deformable transparent anode and cathode, ultraflexible and see‐through polymer LEDs (PLEDs) are demonstrated. The CP‐based PLEDs exhibit outstanding dual‐side light‐outcoupling performance with a high optical transmittance of 75% at a wavelength of 550 nm and with an excellent mechanical durability of 9% bending strain. Moreover, the CP‐based PLEDs fabricated on 4 µm thick plastic foils with all‐solution processing have extremely deformable and foldable light‐emitting functionality. This approach is expected to open a new avenue for developing wearable and attachable transparent displays.     

Solution-processed metal nanowire mesh transparent electrodes

Transparent conductive electrodes are important components of thin-film solar cells, light-emitting diodes, and many display technologies. Doped metal oxides are commonly used, but their optical transparency is limited for films with a low sheet resistance. Furthermore, they are prone to cracking when deposited on flexible substrates, are costly, and require a high-temperature step for the best performance. We demonstrate solution-processed transparent electrodes consisting of random meshes of metal nanowires that exhibit an optical transparency equivalent to or better than that of metal-oxide thin films for the same sheet resistance. Organic solar cells deposited on these electrodes show a performance equivalent to that of devices based on a conventional metal-oxide transparent electrode.     

Review of recent achievements in self-healing conductive materials and their applications

Self-healing materials have attracted increasing attention because of their wide range of applications. It can be expected to offer obvious advantages in conductive materials with self-healing properties, which are regarded as promising candidates for the fabrication of self-healing electronics, energy storage devices, sensors, anticorrosive coating and conductive adhesives. In this review, we focused on recent efforts to develop self-healing conductive composites including their preparation methods, properties and applications. The self-healing conductive materials were presented based on different conductive mediums, such as metal, carbon, conductive polymer, ionic liquids. In addition, their novel applications of the self-healing conductive materials in conductive coatings, energy storage devices and sensors are highlighted. Finally, the future challenges of conductive materials with self-healing properties are proposed.     

Alternative Plasmonic Materials: Beyond Gold and Silver

Materials research plays a vital role in transforming breakthrough scientific ideas into next‐generation technology. Similar to the way silicon revolutionized the microelectronics industry, the proper materials can greatly impact the field of plasmonics and metamaterials. Currently, research in plasmonics and metamaterials lacks good material building blocks in order to realize useful devices. Such devices suffer from many drawbacks arising from the undesirable properties of their material building blocks, especially metals. There are many materials, other than conventional metallic components such as gold and silver, that exhibit metallic properties and provide advantages in device performance, design flexibility, fabrication, integration, and tunability. This review explores different material classes for plasmonic and metamaterial applications, such as conventional semiconductors, transparent conducting oxides, perovskite oxides, metal nitrides, silicides, germanides, and 2D materials such as graphene. This review provides a summary of the recent developments in the search for better plasmonic materials and an outlook of further research directions.