Gravure‐Printed Conversion/Alloying Anodes for Lithium‐Ion Batteries

Recently, printing techniques are increasingly investigated in the field of energy storage, especially for the fabrication of custom-designed batteries. Thanks to its many advantages, the most industrially used gravure printing would offer an innovative boost to printed battery production, even if, to date, such a technique is still not well investigated. In this study, for the first time, gravure printing is successfully used to prepare high-performance conversion/alloying anodes for lithium-ion batteries. A multilayer approach allows obtainment of the desired mass loading (about 1.7 mg cm$^{-2}$), reaching similar mass loadings to those obtained by commonly used lab-scale tape-casting methods, allowing for their comparison. High-quality gravure-printed layers are obtained showing a very high homogeneity, resulting in a high reproducibility of their electrochemical performance, very close to the theoretical value, and a long cycle life (up to 400 cycles). The good results are also due to the ink preparation method, using a ball-milling mix of the powders for disaggregation and homogenization of the starting materials. This work demonstrates the possibility of using the highly scalable gravure printing not only in the industrial manufacturing of printed batteries, but also as a useful tool for the study of new materials

Pressureless sintering of ZnO thin film on plastic substrate via vapor annealing process at near-room temperature

In this work, Vapor Annealing Sintering (VAS) process was introduced for low-cost pressureless producing dense Zinc Oxide (ZnO) thin films deposited from nanoparticles at near-room temperature (50 °C). Spontaneous densification evolution from nanoparticulate to a dense film via a dissolution-diffusion-reprecipitation mechanism was observed exposing ZnO layers to the vapor of an acetic acid aqueous solution at isothermal condition. The influence of the annealing on the optical properties of the treated films was investigated in order to study the structural changes. The proposed method can allow new opportunities for simple and low-cost ceramics thin film manufacturing also involving pressure and temperature-sensitive materials

Electron beam curing technology for very high-throughput manufacturing of flexible alternating current powder electroluminescent devices

Thick-film alternating current powder-based electroluminescent (ACPEL) succeeds on the market as mature technology for large-area light sources. An additional boost for its development may come from the radiation curing technology. Since it is totally compatible with high-speed roll-to-roll processing, radiation curing can offer multiple advantages to further lower costs and make easier the fabrication process of ACPEL devices. In this paper, the application of the electron beam (EB) curing technology to produce flexible ACPEL devices was explored for the first time. In particular, devices with emitting layer made by EB irradiation were successfully fabricated on poly(ethylene terephthalate) (PET) substrate. Device properties were evaluated and compared with those obtained using the conventional ultraviolet curing process. Smaller driving voltages and higher luminous output were observed for the EB treated samples as a consequence of a more cross-linked polymeric binder of the emitting layer generated. In addition, possible effects of EB overdose were also investigated; experiments revealed that excessively high doses can induce the degradation of both polymeric binder and emitting particles. Therefore, the feasibility of using the EB curing was proven to fabricate ACPEL devices, launching it as the next future technology for more sustainable, very fast, and one-step manufacturing of powder-based alternating current EL devices

Evaluation of the stability of different encapsulated blue OLEDs

Organic light emitting diodes (OLEDs) are nowadays the most attractive technology for displays and lighting applications. However, their short lifetime remains the most important limit for their broad commercialization. In particular, blue OLEDs generally present the worst stability respect to the other colors. While the extrinsic degradation can be easily controlled by proper encapsulation, understanding the origins of the intrinsic degradation remains a challenge: up to now, the proposed mechanisms have not considered possible phenomena that can occur during OFF-time periods. In this study, intrinsic degradation phenomena have been studied through shelf life experiments performed at different storage conditions on two types of blue OLEDs. Experiments revealed that physical aging occurs for both types of devices, leading to irreversible time-dependent luminance loss

Low-Temperature Growth of ZnO Nanowires from Gravure-Printed ZnO Nanoparticle Seed Layers for Flexible Piezoelectric Devices

Zinc oxide (ZnO) nanowires (NWs) are excellent candidates for the fabrication of energy harvesters, mechanical sensors, and piezotronic and piezophototronic devices. In order to integrate ZnO NWs into flexible devices, low-temperature fabrication methods are required that do not damage the plastic substrate. To date, the deposition of patterned ceramic thin films on flexible substrates is a difficult task to perform under vacuum-free conditions. Printing methods to deposit functional thin films offer many advantages, such as a low cost, low temperature, high throughput, and patterning at the same stage of deposition. Among printing techniques, gravure-based techniques are among the most attractive due to their ability to produce high quality results at high speeds and perform deposition over a large area. In this paper, we explore gravure printing as a cost-effective high-quality method to deposit thin ZnO seed layers on flexible polymer substrates. For the first time, we show that by following a chemical bath deposition (CBD) process, ZnO nanowires may be grown over gravure-printed ZnO nanoparticle seed layers. Piezo-response force microscopy (PFM) reveals the presence of a homogeneous distribution of Zn-polar domains in the NWs, and, by use of the data, the piezoelectric coefficient is estimated to be close to 4 pm/V. The overall results demonstrate that gravure printing is an appropriate method to deposit seed layers at a low temperature and to undertake the direct fabrication of flexible piezoelectric transducers that are based on ZnO nanowires. This work opens the possibility of manufacturing completely vacuum-free solution-based flexible piezoelectric devices

Size and Semiconducting Effects on the Piezoelectric Performances of ZnO Nanowires Grown onto Gravure-Printed Seed Layers on Flexible Substrates

Zinc oxide (ZnO) nanogenerators have attracted increasing interest in the scientific community for use in energy harvesting and mechanical sensing applications. Understanding the interplay between piezoelectricity and semiconductor physics is fundamental to enhancing these devices’ performances, although direct characterization at the nanoscale is challenging. With this work, we present a new strategy to improve piezoresponse force microscopy (PFM) measurements and analysis. This strategy was applied to study the piezoelectric performances of ZnO nanowires grown on seed layers deposited by gravure printing onto flexible substrates. We demonstrate the influence of nanowire diameter and atomic force microscope (AFM) tip position on the piezoresponse amplitude. We also explain our results with simulations showing the importance of considering semiconducting properties in the analysis