Nickel oxide (NiO) is a wide band gap semiconductor material that is used as an electrochromic layer or an ion storage layer in electrochromic devices. In this work, the effect of annealing temperature on sol-gel NiO films was investigated. Fourier transform infrared spectroscopy (FTIR) showed that the formation of NiO via decomposition of the precursor nickel acetate occurred at about 300 °C. Meanwhile, an increase in roughness was observed by Atomic force microscope (AFM), and precipitation of a large number of crystallites was observed at 500 °C. X-ray Diffraction (XRD) showed that the NiO film obtained at such a temperature showed a degree of crystallinity. The film crystallinity and crystallite size also increased with increasing annealing temperature. An ultraviolet spectrophotometer was used to investigate the optical band gap of the colored NiO films, and it was found that the band gap increased from 3.65 eV to 3.74 eV with the increase in annealing temperature. An electrochromic test further showed that optical modulation density and coloring efficiency decreased with the increase in crystallite size. The electrochromic reaction of the nickel oxide film is more likely to occur at the crystal interface and is closely related to the change of the optical band gap. An NiO film with smaller crystallite size is more conducive to ion implantation and the films treated at 300 °C exhibit optimum electrochromic behavior.

With the rapid development of flexible electronic devices (especially flexible LCD/OLED), flexible transparent electrodes (FTEs) with high light transmittance, high electrical conductivity, and excellent stretchability have attracted extensive attention from researchers and businesses. FTEs serve as an important part of display devices (touch screen and display), energy storage devices (solar cells and super capacitors), and wearable medical devices (electronic skin). In this paper, we review the recent progress in the field of FTEs, with special emphasis on metal materials, carbon-based materials, conductive polymers (CPs), and composite materials, which are good alternatives to the traditional commercial transparent electrode (i.e., indium tin oxide, ITO). With respect to production methods, this article provides a detailed discussion on the performance differences and practical applications of different materials. Furthermore, major challenges and future developments of FTEs are also discussed.

The concept of “high entropy” was first proposed while exploring the unknown center of the metal alloy phase diagram, and then expanded to oxides. The colossal dielectric constant found on the bulk high-entropy oxides (HEOs) reveals the potential application of the high-entropy oxides in the dielectric aspects. Despite the fact that known HEO thin films have not been reported in the field of dielectric properties so far, with the high-entropy effects and theoretical guidance of high entropy, it is predictable that they will be discovered. Currently, researchers are verifying that appropriately increasing the oxygen content in the oxide, raising the temperature and raising the pressure during preparation have an obvious influence on thin films’ resistivity, which may be the guidance on obtaining an HEO film large dielectric constant. Finally, it could composite a metal–insulator–metal capacitor, and contribute to sensors and energy storage devices’ development; alternatively, it could be put into application in emerging thin-film transistor technologies, such as those based on amorphous metal oxide semiconductors, semiconducting carbon nanotubes, and organic semiconductors.

In this work, an innovative all-sputtered bottom-gate thin film transistor (TFT) using an amorphous InGaZnO (IGZO)/Al ₂ O ₃ bi-layer channel was fabricated by fully room temperature processes on a flexible PEN substrate.

The high dielectric constant ZrO₂, as one of the most promising gate dielectric materials for next generation semiconductor device, is expected to be introduced as a new high k dielectric layer to replace the traditional SiO₂ gate dielectric. The electrical properties of ZrO₂ films prepared by various deposition methods and the main methods to improve their electrical properties are introduced, including doping of nonmetal elements, metal doping design of pseudo-binary alloy system, new stacking structure, coupling with organic materials and utilization of crystalline ZrO₂ as well as optimization of low-temperature solution process. The applications of ZrO₂ and its composite thin film materials in metal oxide semiconductor field effect transistor (MOSFET) and thin film transistors (TFTs) with low power consumption and high performance are prospected.

Tungsten trioxide (WO₃) is a wide band gap semiconductor material that is used as an important electrochromic layer in electrochromic devices. In this work, the effects of the annealing temperature on the optical band gap of sol-gel WO₃ films were investigated. X-ray Diffraction (XRD) showed that WO₃ films were amorphous after being annealed at 100 °C, 200 °C and 300 °C, respectively, but became crystallized at 400 °C and 500 °C. An atomic force microscope (AFM) showed that the crystalline WO₃ films were rougher than the amorphous WO₃ films (annealed at 200 °C and 300 °C). An ultraviolet spectrophotometer showed that the optical band gap of the WO₃ films decreased from 3.62 eV to 3.30 eV with the increase in the annealing temperature. When the Li⁺ was injected into WO₃ film in the electrochromic reaction, the optical band gap of the WO₃ films decreased. The correlation between the optical band gap and the electrical properties of the WO₃ films was found in the electrochromic test by analyzing the change in the response time and the current density. The decrease in the optical band gap demonstrates that the conductivity increases with the corresponding increase in the annealing temperature.