Xungang Diao

A new all-thin-film electrochromic device using LiBSO as the ion conducting layer

An all-thin-film electrochromic device glass/ITO/NiOx/LiBSO/WO3/ITO was fabricated by magnetron sputtering, in which LiBO2 + Li2SO4 (LiBSO) was used as the new ion conducting layer. The average visible light transmittances of bleached and coloured states reached 56.8% and 4.6%, respectively, and the optical transmittance modulation can reach 52.2%. The effect of substrate temperature on the device performance was investigated by comparing liquid nitrogen cooling and water cooling. The results showed that the device had a better electrochromic performance when fabricated at a low substrate temperature.

Highly Efficient Gating of Electrically Actuated Nanochannels for Pulsatile Drug Delivery Stemming from a Reversible Wettability Switch

Many ion channels in the cell membrane are believed to function as gates that control the water and ion flow through the transitions between an inherent hydrophobic state and a stimuli-induced hydration state. The construction of nanofluidic gating systems with high gating efficiency and reversibility is inspired by this hydrophobic gating behavior. A kind of electrically actuated nanochannel is developed by integrating a polypyrrole (PPy) micro/nanoporous film doped with perfluorooctanesulfonate ions onto an anodic aluminum oxide nanoporous membrane. Stemming from the reversible wettability switch of the doped PPy film in response to the applied redox potentials, the nanochannels exhibit highly efficient and reversible gating behaviors. The optimized gating ratio is over 105 , which is an ultrahigh value when compared with that of the existing reversibly gated nanochannels with comparable pore diameters. Furthermore, the gating behavior of the electrically actuated nanochannels shows excellent repeatability and stability. Based on this highly efficient and reversible gating function, the electrically actuated nanochannels are further applied for drug delivery, which achieves the pulsatile release of two water-soluble drug models. The electrically actuated nanochannels may find potential applications in accurate and on-demand drug therapy.

Preparation and properties of all-solid-state inorganic thin film glass/ITO/WO3/LiNbO3/NiOx/ITO electrochromic device

The all-thin-film inorganic electrochromic device (ECD) with LiNbO3 as the ion conductor layer was prepared. The ECD was fabricated monolithically in a same vacuum chamber layer by layer using DC reactive sputtering for WO3, NiOx and ITO, and radio frequency (RF) sputtering for LiNbO3. The properties and performance of WO3 thin film and the ECD were studied through X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible spectrometry. WO3 thin film has more than 60% optical modulation with porous amorphous structure. The visible transmittance modulation of the ECD is more than 65%, and the response time of coloring and bleaching are 45 s and 25 s, respectively.

Electro-optical performance of inorganic monolithic electrochromic device with a pulsed DC sputtered Li x Mg y N ion conductor

Lithium magnesium nitride (LixMgyN) thin films were deposited by pulsed DC reactive magnetron sputtering from a LiMg alloy target in the mixture gas of Ar and N2. The as-prepared LixMgyN films were amorphous. A monolithic inorganic electrochromic device (ECD) based on WO3/NiO complementary structure was fabricated using the LixMgyN as the ion conductor layer. The addition of a 150-nm thick Si3N4 buffer layer between LixMgyN and NiO made coloration and bleaching reversible and stable. Electrochemical and optical characterizations were conducted to evaluate the performance of the ECD. Electro-optical data were recorded for both 1000 chronoamperometric cycles and 1000 voltammetric cycles. Activation and degradation of the electro-optical properties of the ECD were observed.

Lithium trapping as a degradation mechanism of the electrochromic properties of all-solid-state WO3//NiO devices

There has been keen interest for years in the research of all-solid-state transmittance-type electrochromic (EC) devices due to their various applications especially in ‘‘smart windows’’. A step forward has been taken in the successful preparation of full multilayered devices with enlarged optical contrast and fast switching response. However, limited durability remains a severe issue. Upon cycling, EC devices suffer from decline of charge capacity as well as optical modulation while the detailed degradation mechanisms remain poorly understood. Here, we demonstrate unambiguous ion-trapping evidence to interpret the charge density decay of the EC device induced using various voltammetric cycling protocols, namely long-term cycling and accelerated cycling. Pronounced comparable ion trapping occurs in cathodically colored WO3 films whatever the cycling procedure is, suggesting the existence of the trapping ‘‘saturation’’ phenomenon. From second-ion-mass-spectroscopy analysis, the 7Li+/184W+ ratio in the degraded WO3 films is more than 100 while it is almost zero in the as-prepared films. In contrast, for anodically colored NiO, a larger number of trapped cations is determined in the long-term cycled films than in the accelerated ones. In combination with X-ray-photoelectron-spectroscopy, variable bonding energies indicate that the ions are trapped at different types of sites, depending on the cycling procedure, and they can reside in the structural channels or break the network chains to form new chemical bondings, thus resulting in a significant color difference. In addition, a clear upward trend in the trapped Li concentration along with depth is observed. All our findings provide a deep insight into the degradation phenomenon taking place in electrochromic films as well as in full devices and offer valuable information for the understanding of micro mechanisms.

Improved performance of all-thin-film electrochromic devices with two ZrO2 protective layers

To improve the overall electrochromic properties of the all-thin-film electrochromic devices (ECDs), the seven-layer-structure ITO/NiOx/ZrO2/ZrO2:H/ZrO2/WO3/ITO were fabricated by DC reactive magnetron sputtering at room temperature. The X-ray diffraction and ultraviolet-visible (UV) optical spectra were characterized to elaborate the effects of ZrO2 protective layers on the optical modulation, cycling stability, and the weather fastness of the electrochromic devices. At the same time, the devices without ZrO2 protective layer were prepared in the same method as comparison. In XRD analysis, the insertion of hydrogen atoms does not bring significant distortion inside the crystalline structure of ZrO2 film which ensures that ZrO2 and ZrO2:H film can match well. The transmittance spectra show that the optical modulation of both ECDs was roughly identical which demonstrates no color effect of ZrO2 film on electrochromic device. After cycling for 1000xa0cycles, the attenuation rate of optical modulation of devices with protective layer is 31.6% which is far less than that of devices without protective layer (63.7%). After storage for 18xa0days in natural conditions, the protective layer can guarantee that electrochromic device steadily works with the △T of around 43.0% in the first 100xa0cycles; whereas, the △T of the device without protective layer decreases rapidly from 51 to 14.7%. Thus, these ZrO2 protective layers show considerable improvements in continuous cyclic stability and the natural self-attenuation performance.

Mechanistic Insights into the Coloration, Evolution, and Degradation of NiOx Electrochromic Anodes

NiO x is recognized as the leading candidate for smart window anodes that can dynamically modulate optical absorption, thereby achieving energy efficiency in construction buildings. However, the electrochromic mechanism in NiO x is not yet clear, and the ionic species involved are sometimes ambiguous, particularly in aprotic electrolytes. We demonstrate herein that the net coloration effect originates from newly generated high-valence Ni3+/Ni4+ ions during anion-dependent anodization, and the Li+ intercalation/deintercalation only plays a role in modulating the oxidation state of Ni. Unambiguous evidencesxa0xa0proving the occurrence of anodization reactionxa0were obtained by both chronoamperometry and cyclic voltammetry. Benefiting from the irreversible polarization of Ni2+ to Ni3+/Ni4+, the quantity of voltammetric charge increases by ∼38% under the same test conditions, enhancing the corresponding electrochromic modulation by ∼8%. Strong linkages between the coloration, evolution, and degradation observed in this work provide in-depth insights into the electrocatalytic and electrochromic mechanisms.

Robust Sandwich-Structured Nanofluidic Diodes Modulating Ionic Transport for an Enhanced Electrochromic Performance

Abstract Biomimetic solid‐state nanofluidic diodes have attracted extensive research interest due to the possible applications in various fields, such as biosensing, energy conversion, and nanofluidic circuits. However, contributions of exterior surface to the transmembrane ionic transport are often ignored, which can be a crucial factor for ion rectification behavior. Herein, a rational design of robust sandwich‐structured nanofluidic diode is shown by creating opposite charges on the exterior surfaces of a nanoporous membrane using inorganic oxides with distinct isoelectric points. Potential‐induced changes in ion concentration within the nanopores lead to a current rectification; the results are subsequently supported by a theoretical simulation. Except for providing surface charges, functional inorganic oxides used in this work are complementary electrochromic materials. Hence, the sandwich‐structured nanofluidic diode is further developed into an electrochromic membrane exhibiting a visual color change in response to redox potentials. The results show that the surface‐charge‐governed ionic transport and the nanoporous structure facilitate the migration of Li+ ions, which in turn enhance the electrochromic performance. It is envisioned that this work will create new avenues to design and optimize nanofluidic diodes and electrochromic devices.

A Novel Inorganic Ion Conductor Electrochromic Device: MoO3/LiAlO2/NiOx

An all-thin-film glass/ITO/MoO3/LiAlO2/NiOx/ITO device was deposited by magnetron sputtering for electrochromic application. The amorphous MoO3 and LiAlO2 thin films were prepared with the substrate temperature below 0 °C and in O2 and Ar gas pressure. The structure and surface morphology of the films were characterized by x-ray diffraction (XRD) and atomic force microscopy (AFM). It has been found that the amorphous LiAlO2 thin film was a suitable ion conductor for the electrochromic device. The transmittance in the wavelength range of 400-800 nm for the ITO/MoO3/LiAlO2/NiOx/ITO device changed from 14.48 % to 57.68 % by the applied voltage of 7 V. The blue-colored electrochromic property could be observed for the all-thin-film device. The experimental results indicated that such a monolithic system had great potential to be applied in flat-panel displays and smart windows.