High-efficiency robust perovskite solar cells on ultrathin flexible substrates.

Wide applications of personal consumer electronics have triggered tremendous need for portable power sources featuring light-weight and mechanical flexibility. Perovskite solar cells offer a compelling combination of low-cost and high device performance. Here we demonstrate high-performance planar heterojunction perovskite solar cells constructed on highly flexible and ultrathin silver-mesh/conducting polymer substrates. The device performance is comparable to that of their counterparts on rigid glass/indium tin oxide substrates, reaching a power conversion efficiency of 14.0%, while the specific power (the ratio of power to device weight) reaches 1.96 kW kg(-1), given the fact that the device is constructed on a 57-μm-thick polyethylene terephthalate based substrate. The flexible device also demonstrates excellent robustness against mechanical deformation, retaining >95% of its original efficiency after 5,000 times fully bending. Our results confirmed that perovskite thin films are fully compatible with our flexible substrates, and are thus promising for future applications in flexible and bendable solar cells

Applications of Carbon Nanotubes to Flexible Transparent Conductive Electrodes

Transparent conductive electrodes (TCEs) have attracted great interest because of their wide range of applications in solar cells, liquid crystal displays (LCDs), organic light-emitting diodes (OLEDs), and touch screen panels (TSPs). Indium-tin-oxide (ITO) thin films as TCEs possess exceptional optoelectronic properties, but they have several disadvantages such as a brittle nature due to their low fracture strain and lack of flexibility, a high processing temperature that damages the flexible substrates, low adhesion to polymeric materials, and relative rarity on Earth, which makes their price unstable. This has motivated several research studies of late for developing alternative materials to replace ITO such as metal meshes, metal nanowires, conductive polymers, graphene, and carbon nanotubes (CNTs). Out of the abovementioned candidates, CNTs have advantages in chemical stability, thermal conductivity, mechanical strength, and flexibility. However, there are still several problems yet to be solved for achieving CNT-based flexible TCEs with excellent characteristics and high stability. In this chapter, the properties of CNTs and their applications especially for flexible TCEs are presented, including the preparation details of CNTs based on solution processes, the surface modification of flexible substrates, and the various types of hybrid TCEs based on CNTs

An antireflection transparent conductor with ultralow optical loss (o2 %) and electrical resistance (o6O 2)

Transparent conductors are essential in many optoelectronic devices, such as displays, smart windows, light-emitting diodes and solar cells. Here we demonstrate a transparent conductor with optical loss of B1.6%, that is, even lower than that of single-layer graphene (2.3%), and transmission higher than 98% over the visible wavelength range. This was possible by an optimized antireflection design consisting in applying Al-doped ZnO and TiO2 layers with precise thicknesses to a highly conductive Ag ultrathin film. The proposed multilayer structure also possesses a low electrical resistance (5.75O 2), a figure of merit four times larger than that of indium tin oxide, the most widely used transparent conductor today, and, contrary to it, is mechanically flexible and room temperature deposited. To assess the application potentials, transparent shielding of radiofrequency and microwave interference signals with B30 dB attenuation up to 18 GHz was achieved.Peer ReviewedPostprint (author's final draft

Transparent conducting film fabricated by metal mesh method with Ag and cu@ag mixture nanoparticle pastes

Transparent conducting electrode film is highly desirable for application in touch screen panels (TSPs), flexible and wearable displays, sensors, and actuators. A sputtered film of indium tin oxide (ITO) shows high transmittance (90%) at low sheet resistance (50 ??/cm2). However, ITO films lack mechanical flexibility, especially under bending stress, and have limitation in application to large-area TSPs (over 15 inches) due to the trade-off in high transmittance and low sheet resistance properties. One promising solution is to use metal mesh-type transparent conducting film, especially for touch panel application. In this work, we investigated such inter-related issues as UV imprinting process to make a trench layer pattern, the synthesis of core-shell-type Ag and Cu@Ag composite nanoparticles and their paste formulation, the filling of Ag and Cu@Ag mixture nanoparticle paste to the trench layer, and touch panel fabrication processes

Electrical conductivity of crack-template-based transparent conductive films: A computational point of view

Crack-template-based transparent conductive films (TCFs) are promising kinds of junction-free, metallic network electrodes that can be used, e.g., for transparent electromagnetic interference (EMI) shielding. Using image processing of published photos of TCFs, we have analyzed the topological and geometrical properties of such crack templates. Additionally, we analyzed the topological and geometrical properties of some computer-generated networks. We computed the electrical conductance of such networks against the number density of their cracks. Comparison of these computations with predictions of the two analytical approaches revealed the proportionality of the electrical conductance to the square root of the number density of the cracks was found, this being consistent with the theoretical predictions.Comment: 12 pages, 10 figures, 3 tables, 51 reference

A Review of Conductive Metal Nanomaterials as Conductive, Transparent, and Flexible Coatings, Thin Films, and Conductive Fillers: Different Deposition Methods and Applications

With ever-increasing demand for lightweight, small, and portable devices, the rate of production of electronic and optoelectronic devices is constantly increasing, and alternatives to the current heavy, voluminous, fragile, conductive and transparent materials will inevitably be needed in the future. Conductive metal nanomaterials (such as silver, gold, copper, zinc oxide, aluminum, and tin) and carbon-based conductive materials (carbon nanotubes and graphene) exhibit great promise as alternatives to conventional conductive materials. Successfully incorporating conductive nanomaterials into thin films would combine their excellent electrical and optical properties with versatile mechanical characteristics superior to those of conventional conductive materials. In this review, the different conductive metal nanomaterials are introduced, and the challenges facing methods of thin film deposition and applications of thin films as conductive coatings are investigated

DIRECT PRINTING/COATING/PLATING OF KEY COMPONENTS FOR ELECTRONIC DEVICES

Miniaturization has been a technological trend for several decades for electronic devices. From the practical point of view, the successful miniaturization of fully integrated systems mainly depends on their components. This dissertation examines the inkjet printing of copper oxide inks on flexible substrates for applications in microfluidic valving systems. We expand the knowledge of low-cost and high-performance electrowetting valves and fabricate the microfluidic device for fluidic control, which is necessary to enable the next-generation microfluidic devices. In addition, we also study the electromagnetic interference (EMI) shielding material, which is a crucial part of electronic devices. The basic theory of EMI shielding is discussed in this dissertation. We explore the high-performance shielding materials with novel fabrication methods, such as spray coating, laser carbonizing and electroplating. Chapter 1 describes the fabrication of flexible inkjet-printed copper electrowetting valves. We study the effects of dielectric layer thickness as well as applied voltage to the contact angle decreasing process. Taking this one step further, an electrowetting valve with two controlled channels is described for demonstration. Chapter 2 explores the fabrication of high-performance EMI shielding material of silver-coated carbon fiber fabrics (CFFs) via spray coating. EMI shielding theory is discussed in detail. The silver/CFF composite material is introduced at the lab-scale as well as at the roll-to-roll large fabrication scale. Chapter 3 introduces the high-performance optically transparent copper mesh. The laser carbonizing and electroplating techniques are described. We study the effect of different patterns to the EMI shielding performance. Chapter 4 evaluates the EMI shielding performance of graphite/polymer composites. Microwave exfoliation and acid treatment are explained from the mechanism aspect. Furthermore, future work is described for potential improvement on their performance

Microstructured transparent conductive metallic electrodes fabricated by colloidal lithography

This thesis focuses on the development and optimization of a technique known as self-assembly colloidal lithography (CL) to fabricate transparent conductive electrodes. These contacts are of utmost importance for high performance optoelectronic devices, such as thin film solar cells. As of this moment, indium tin oxide (ITO) is the preferred transparent conductive oxide (TCO), but to improve the cell efficiency new materials with lower sheet resistance and better optical properties should be used. Besides, ITO is relatively expensive, so alternative Earth-abundant materials are highly desired to improve the devices’ cost-effectiveness. Conductive metallic micro-meshes within two thin TCO layers were investigated to improve the sheet resistance while maintaining an anti-reflection coating (ARC) type layer. The meshes were fabricated by CL after studying the influence of the main process parameters: polystyrene sphere sizes, etching times, aluminum and silver for the mesh and indium zinc oxide (IZO) and aluminum zinc oxide (AZO) for the TCO layer were studied. The resulting contacts were analyzed through UV-VIS-NIR spectrophotometry, hall-effect, scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and atomic force microscopy (AFM). The results showed that 1.6 μm precursor spheres etched for 150s were the most reliable to produce closely-packed structures and to obtain low sheet resistance, while 5 μm spheres etched for 120s showed the best optical performance over the UV-VIS-NIR range. The contacts which showed the best optical and electrical results were produced with silver and IZO: when produced with 1.6 μm spheres the contacts presented sheet resistances as low as 10.6 Ω/sq and transmittances up to 75 %, and when produced with 5 μm spheres obtained transmittance up to 85 % with sheet resistance of 121 Ω/sq. The results reveal that our innovative large-area micro-meshed metallic electrodes fabricated by CL can attain performances close to those off state-of-art ITO (10 Ω/sq for 80 % transmittance and 100 Ω/sq for 90 % transmittance), but with superior transmittance mainly in the near-infrared range. This can be highly interesting, for instance, for the intermediate electrodes in multi-terminal multi-junction solar cell architectures

Colloidal-structured metallic micro-grids: High performance transparent electrodes in the red and infrared range

project PON_206_2 project PRN 2014/2020 ALTALUZ (PTDC/CTM-ENE/5125/2014 PTDC/NAN-OPT/28430/2017 PTDC/NAN-OPT/28837/2017 PTDC/EAM-PEC/29905/2017 SFRH/BPD/114833/2016 SFRH/BPD/115566/2016One of the most promising approaches to produce industrial-compatible Transparent Conducting Materials (TCMs) with excellent characteristics is the fabrication of TCO/metal/TCO multilayers. In this article, we report on the electro-optical properties of a novel high-performing TCO/metal/TCO structure in which the intra-layer is a micro-structured metallic grid instead of a continuous thin film. The grid is obtained by evaporation of Ag through a mask of polystyrene colloidal micro-spheres deposited by the Langmuir-Blodgett method and partially dry-etched in plasma. IZO/Ag grid/IZO structures with different thicknesses and mesh dimensions have been fabricated, exhibiting excellent electrical characteristics (sheet resistance below 10 Ω/□) and particularly high optical transmittance in the near-infrared spectral region as compared to planar (unstructured) TCM multilayers. Numerical simulations were also used to highlight the role of the Ag mesh parameters on the electrical properties.preprintpublishe