Photochemistry in the Low-Temperature Processing of Metal Oxide Thin Films by Solution Methods

Photochemistry has emerged in the last few years as a powerful tool for the low-temperature processing of metal oxide thin films prepared by solution methods. Today, its implementation into the fabrication procedure makes possible the integration of amorphous semiconductors or functional crystalline oxides into flexible electronic systems at temperatures below 350 °C. In this review, the effects of UV irradiation at the different stages of the chemical solution deposition of metal oxide thin films are presented. These stages include from the synthesis of the precursor solution to the formation of the amorphous metal-oxygen network in the film and its subsequent crystallization into the oxide phase. Photochemical reactions that can be induced in both the solution deposited layer and the irradiation atmosphere are first described, highlighting the role of the potential reactive chemical species formed in the system under irradiation, such as free radicals or oxidizing compounds. Then, the photochemical effects of continuous UV light on the film are shown, focusing on the decomposition of the metal precursors, the condensation and densification of the metal-oxygen network, and the nucleation and growth of the crystalline oxide. All these processes are demonstrated to advance the formation and crystallization of the metal oxide thin film to an earlier stage, which is ultimately translated into a lower temperature range of fabrication. The reduced energy consumption of the process upon decreasing the processing temperature, and the prospect of using light instead of heat in the synthesis of inorganic materials, make photochemistry as a promising technique for a sustainable future ever more needed in our life.     

Solution‐Phase Conversion of Bulk Metal Oxides to Metal Chalcogenides Using a Simple Thiol–Amine Solvent Mixture

A thiol–amine solvent mixture is used to dissolve ten inexpensive bulk oxides (Cu₂O, ZnO, GeO₂, As₂O₃, Ag₂O, CdO, SnO, Sb₂O₃, PbO, and Bi₂O₃) under ambient conditions. Dissolved oxides can be converted to the corresponding sulfides using the thiol as the sulfur source, while selenides and tellurides can be accessed upon mixing with a stoichiometric amount of dissolved selenium or tellurium. The practicality of this method is illustrated by solution depositing Sb₂Se₃ thin films from compound inks of dissolved Sb₂O₃ and selenium that give high photoelectrochemical current response. The direct band gap of the resulting material can be tuned from 1.2–1.6 eV by modulating the ink formulation to give compositionally controlled Sb₂Se_3?xS_x alloys.     

Flexible and Epitaxial Metal Oxide Thin Film Growth by Photoreaction Processing for Electrical and Optical Applications

This review summarizes the use of photoreactions that replace conventional heating processes for growing oxide thin films from chemical solutions. In particular, this review outlines key variables in photoreactions that affect epitaxial and polycrystalline thin film growth, including precursor materials, laser wavelength, laser fluence, and carbon. In addition, the features of the photoreaction process that can be controlled at a low temperature by oxygen non-stoichiometry are examined. Likewise, functions that are neither achieved by developing a gradient structure nor controlled by a thermal equilibrium reaction are detailed. Two new concepts are presented, known as photoreaction of nanoparticles (PRNP) and photoreaction of a hybrid solutions (PRHS), in which crystal nuclei are pre-dispersed in a metal–organic compound film. This method has successfully produced flexible phosphor films used as resistor or thermistor electronic components. Finally, thin film growth using different light sources such as flash lamps and femtosecond lasers (fs) is explored.     

溶液法制备柔性压阻式传感器的研究进展

柔性压阻式传感器具有结构简单、易于制备、检测范围广等优势, 在可穿戴电子器件领域中扮演着非常重要的角色. 在制备柔性压阻式传感器的众多方法中, 溶液法由于操作简单、反应条件温和、材料的适用性广泛、易于规模化制备等优势, 成为极具发展前景的制备工艺. 在此基础上, 如何进一步提高柔性压阻式传感器的力学与电学性能也成为研究者们更加关注的话题. 另外, 制备图案化、微型化、规模化的传感器阵列为柔性压阻式传感器的应用范围拓展了新的道路. 本综述首先介绍了柔性压阻式传感器的工作原理与性能指标, 同时讨论了其性能指标对传感器在实际应用中的影响. 随后, 简单介绍了其构成材料, 并通过梳理近年来溶液法制备柔性传感器的研究成果, 选取了几种典型的溶液法制备方法进行重点介绍, 指出其具备的优势及目前存在的问题. 最后, 对溶液法制备柔性传感器的发展方向进行总结与展望.     

Low-Temperature Solution Crystallization of Nanostructured Oxides and Thin Films

As an introduction to this themed issue, a critically selected overview of recent progress on the topic of solution methods for the low-temperature crystallization of nanoscale oxide materials is presented. It is focused on the low-temperature solution processing of oxide nanostructures and thin films. Benefits derived from these methods span from minimizing the environmental impact to reducing the fabrication costs. In addition, this topic is regarded as a key objective in the area because it offers a unique opportunity for the use of these materials in areas like flexible electronics, energy conversion and storage, environmental sciences, catalysis, or biomedicine.     

Flexible active matrix addressed displays manufactured by printing and coating techniques

A flexible electrochromic active matrix addressed display, including 8 × 8 pixels, is demonstrated by using solution processing based on standard printing and coating manufacturing techniques. Each organic electrochromic display (OECD) pixel and its corresponding organic electrochemical transistor (OECT) are located on different sides of the flexible PET substrate. Electronic vias generated through the plastic substrate connects each OECD pixel with one addressing OECT. When comparing this display with actively addressed OECDs with all its components located on the same side, the present approach based on this electronic via substrate provides an enhanced pixel resolution and a relatively more simplified manufacturing process. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Reliable stretchable gold interconnects in biocompatible elastomers

One of the key issues in realization of stretchable and curvilinear electronics is the fabrication of stretchable interconnects. Stretchable interconnects are basically conductor lines embedded in elastomer substrates. Currently, metal interconnects embedded in polydimethylsiloxane are one of the major candidates. In this work, a novel straightforward method is presented that allows the fabrication of 20 μm wide stretchable gold interconnects starting from commercial double sided flexes (Cu–PI–Cu). These interconnects are still fully functional after a minimum of 100 k cycles at 40% elongation. In addition to outstanding reliability in this method of fabrication, fine pitch and biocompatibility are the added values paving the way for medical grade stretchable electronics. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Molecular and Electronic‐Structure Basis of the Ambipolar Behavior of Naphthalimide–Terthiophene Derivatives: Implementation in Organic Field‐Effect Transistors

A new family of naphthalimide‐fused thienopyrazine derivatives for ambipolar charge transport in organic field‐effect transistors is presented. Their electronic and molecular structures were elucidated through optical and vibrational spectroscopy aided by DFT calculations. The results indicate that these compounds have completely planar molecular skeletons which promote good film crystallinity and low reorganization energies for both electron and hole transport. Their performance in organic field‐effect transistors is compared with twisted and planar naphthaleneamidine monoimide‐fused terthiophenes in order to understand the origin of ambipolarity in this new series of molecular semiconductors.     

Transparent Electrodes Printed with Nanocrystal Inks for Flexible Smart Devices

Transparent electrodes (TEs) are crucial in a wide range of modern electronic and optoelectronic devices. However, traditional TEs cannot meet the requirements of smart devices under development in unique fields, such as electronic skins, wearable electronics, robotic skins, flexible and stretchable displays, and solar cells. Emerging TEs printed with nanocrystal (NC) inks are inexpensive and compatible with solution processes, and have huge potential in flexible, stretchable, and wearable devices. Every development in ink‐based electrodes makes them more competitive for practical applications in various smart devices. Herein, we provide an overview of emergent ink‐based electrodes, such as transparent conducting oxides, metal nanowires, graphene, and carbon nanotubes, and their application in solution‐based flexible and stretchable devices.     

PEDOT导电高分子在柔性能量转化与存储器件的研究进展

近年来,柔性有机和钙钛矿光伏器件、有机薄膜晶体管和医用传感器等因其具有可穿戴性、柔性、半透明性等优点,成为科学研究的热门领域.利用具有优异力学性能的导电聚合物是实现这些高性能器件的有效途径之一.在导电聚合物中,3,4-亚乙基二氧噻吩(PEDOT)及其水性分散液3,4-亚乙基二氧噻吩:聚苯乙烯磺酸盐(PEDOT:PSS)...     

Thiophene polymer semiconductors for organic thin-film transistors

Printed organic thin-film transistors (OTFTs) have received great interests as potentially low-cost alternative to silicon technology for application in large-area, flexible, and ultra-low-cost electronics. One of the critical materials for TFTs is semiconductor, which has a dominant impact on the transistor properties. We review here the structural studies and design of thiophene-based polymer semiconductors with respect to solution processability, ambient stability, molecular self-organization, and field-effect transistor properties for OTFT applications. We show that through judicial monomer design, delicately controlled pi-conjugation, and strategically positioned pendant side-chain distribution, novel solution-processable thiophene polymer semiconductors with excellent self-organization ability to form extended lamellar pi-stacking orders can be developed. OTFTs using semiconductors of this nature processed in ambient conditions have provided excellent field-effect transistor properties.     

A low-temperature X-ray diffraction study of the Cu2ZnSnSe4 thin films

Low-temperature XRD measurements were performed to confirm the phase composition and structural parameters of the electrochemically deposited Cu₂ZnSnSe₄ thin films on flexible metal substrates.     

Highly Conductive Films of Layered Ternary Transition‐Metal Nitrides

Film studies : Epitaxial films of BaZrN₂ (see TEM image) and BaHfN₂ are grown by polymer‐assisted deposition on SrTiO₃ (STO) substrates. The films are phase‐pure, allowing the intrinsic physical properties of the ternary nitrides to be studied. From 5 to 300 K, the films exhibit metallic‐like resistivity–temperature behavior, with large residual resistivity ratios.

     

A Flexible Rechargeable Zinc–Air Battery with Excellent Low‐Temperature Adaptability

Flexible zinc–air batteries (ZAB) are a promising battery candidate for emerging flexible electronic devices, but the catalysis‐based working principle and unique semi‐opened structure pose a severe challenge to their overall performance at cold temperature. Herein, we report the first flexible rechargeable ZAB with excellent low‐temperature adaptability, based on the innovation of an efficient electrocatalyst to offset the electrochemical performance shrinkage caused by decreased temperature and a highly conductive hydrogel with a polarized terminal group to render the anti‐freezing property. The fabricated ZABs show excellent electrochemical performances that outperform those of many aqueous ZABs at room temperature. They also deliver a high capacity of 691 mAh g^?1 and an energy density of 798 Wh kg^?1 at ?20 °C (92.7 % and 87.2 % retention of the room temperature counterparts, respectively), together with excellent flexibility and reverting capability.     

金属β－二酮化合物用于MOCVD法生长铁电氧化物薄膜

对用于MOCVD法生长铁电氧化物薄膜的金属β－二酮化合物的制备、结构及性质进行了评述，对它们在生长铁电薄膜中的应用现状进行了介绍，并对它们的应用前景作了展望。