All-solid-state inorganic electrochromic devices (ECD) typically suffer from the leakage current which mainly arises from bulk defects and pinholes particularly in the ion conducting layer. The leakage current can lead to rapid self-bleaching of the ECD under open circuit, increased power consumption, and inhomogeneous coloration. Silicon nitride (Si3N4) thin films were prepared by pulsed DC reactive magnetron sputtering, and integrated into a monolithic inorganic ECD to reduce the leakage current. The device was prepared by a series of sputtering processes and the layer stacks were Glass/ITO/NiO/Si3N4/LiNbO3/Si3N4/WO3/ITO. The optimization of Si3N4 single layer was studied by electrochemical cyclic voltammetry. The effects of leakage current on electrical and optical properties of the ECDs were studied by chronoamperometry and cyclic voltammetry. The leakage current of the device is reduced from 216.0 to 32.1 μA/cm2 with two 80nm-thick Si3N4 layers, and the open circuit memory effect is significantly improved. The optical modulation is 43% at 550 nm by applied voltages of −2.0 V and 1.5 V.

Polyvinyl butyral-based gel polymer electrolyte films (PVB-based GPEFs) were prepared by casting method. The surface morphology and ionic conductivity of the PVB-based GPEFs were measured; cyclic voltammetry behavior, optical properties, and coloration efficiency of the devices were investigated. The SEM shows amorphous polymer matrix with interval and micropores among the molecule chains. With different volume of ionic liquid, the ionic conductivity of electrolyte films increased up to 4.0 × 10−-5 and 6.2 × 10−5 S/cm at 25 and 50 °C, respectively. Electrochromic devices (ECDs) with glass/ITO/WO3/PVB-based GPEF/Ni1-xO/ITO/glass configuration were prepared following the technology of laminated safety glass. The best device provided excellent electrochromic performances with high optical modulation of 65.8% at 550 nm, coloration efficiency of 175.34 cm2/C, and long-term stability. In addition, small color fading of 4.8% was observed under self-discharging conditions for 16 h, proving that the PVB-based ECD possesses sufficient memory effect as smart window.

•A wide-angle absorptance coating with α = 0.945 was obtained.•Annealing at 600 °C in vacuum is beneficial to enhance thermal stability.•Degradation of conversion efficiency is occurred after annealing at 800 °C.•Degradation can be attributed to grain growth and inter-diffusion.In this paper, the angular solar absorptance of Mo–SiO2 double cermet solar selective absorber coating was simulated based on the deduced optical constants and calculated from measured reflectance spectra in the wavelength range 0.25–2.5 μm for incidence angles between 0° and 75° by interval of 15°. It was found that Mo–SiO2 double cermet solar selective absorber with angular absorptance α = 0.945 from 0° up to 60° is a wide-angle absorptance coating. The effect of thermal annealing on optical properties, microstructure and morphology of Mo–SiO2 double cermet solar selective coating was investigated. The annealing in vacuum at 600 °C results in grain refinement of Mo particle, denser cermet layer and photo-thermal conversion efficiency increasing of 0.6%. Annealing at 800 °C leads to grain growth of polycrystalline structure Mo, inter-diffusion in cermet layer and the photo-thermal conversion efficiency decreasing of 1.3%.

•An inorganic all-thin-film ECD was fabricated by magnetron sputtering.•Monolithic process was smoothly adopted to prepare flexible electrochromic device.•The flexible ECD has a high optical modulation and coloration efficiency.In this study, an all-thin-film inorganic electrochromic device was monolithically fabricated on a 10 cm×8 cm flexible PET/ITO substrate by magnetron sputtering process at room temperature. The device has a complementary structure and consists of five thin films. Tungsten oxide (WO3) and nickel oxide (NiOx) act individually as complementary electrochromic layers. Lithium tantalate (LiTaO3) plays the role of Li+ ions conductor layer and both indium tin oxides (ITO) are adopted as inter-counter transparent conductive electrodes. The complementary device with configuration ITO/NiOx/LiTaO3/WO3/ITO has high optical modulation approximating 63% in the range from 400 to 1600 nm and shows the coloration efficiency as high as 68.5 cm2 C−1. In addition, the response characteristic is investigated for the electrochromic process.

•NiOx films sputtered in diverse O2 atmosphere were applied in all-thin-film ECDs.•Various compositions, microstructures and transmittance of the films were tested.•ECDs with NiOx prepared in 6% and 4.5% O2 content had higher optical modulation.•ECD with NiOx prepared in 6% had faster switching responses than that in 4.5%.Nickel oxides (NiOx) thin films were magnetron sputtered in Ar/O2 mixing gases with the relative O2 concentration varied from 4.5% to 20%. Subsequently, each NiOx film was used to fabricate an all-thin-film glass/ITO/NiOx/LiTaO3/WO3/ITO electrochromic device (ECD). All the ECDs were fabricated monolithically in a same vacuum chamber layer by layer using dc reactive sputtering for NiOx, WO3 and ITO, and radio frequency (rf) sputtering for LiTaO3. Influence of oxygen concentration upon properties of NiOx as well as their corresponding ECDs was focused on and studied through grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible spectrometry. The results show that the as-prepared nickel oxide films can be represented as NiOx with 1.10 ≤ x ≤ 1.21 when O2 concentration in sputtering gas changes. With increasing x, the preferred crystalline orientation (100) of NiOx thin films vanished, and (111) and (220) plane appeared. Owing to the poor crystalline structure in favor of ion transportation in the NiOx layer and less proportion of Ni3+, the device with NiOx film deposited at 6% O2 concentration displayed high transmittance at bleached state and subsequently an excellent transmittance modulation of more than 67%. Coloring and bleaching response time of this device was 85 s and 42 s, respectively. The results confirm that the magnetron-sputtered technical parameters proposed in this work is promising for all-thin-film ECDs with excellent electrochromic performance.

Indium tin oxide (ITO) films were deposited on glass substrates by rf magnetron sputtering using a ceramic target (In2O3–SnO2, 90–10 wt%) without extra heating. The post annealing was done in air and in vacuum, respectively. The effects of annealing on the structure, surface morphology, optical and electrical properties of the ITO films were studied. The results show that the increase of the annealing temperature improves the crystallinity of the films, increases the surface roughness, and improves the optical and electrical properties. The transmittance of the films in visible region is increased over 90% after the annealing process in air or in vacuum. The resistivity of the films deposited is about 8.125×10−4 Ω cm and falls down to 2.34×10−4 Ω cm as the annealing temperature is increased to 500°C in vacuum. Compared with the results of the ITO films annealed in air, the properties of the films annealed in vacuum is better.