The AC-electronic and dielectric properties of different phthalocyanine films (ZnPc, CuPc, FePc, and H₂Pc) were investigated over a wide range of temperature. Both real and imaginary parts of the dielectric constant (ε=ε₁-iε₂) were found to be influenced by temperature and frequency. Qualitatively the behavior was the same for those compounds; however, the central atom, film thickness, and the electrode type play an important role in the variation of their values.The relaxation time, τ, was strongly frequency-dependent at all temperatures and low frequencies, while a weak dependency is observed at higher frequencies. The relaxation activation energy was derived from the slopes of the fitted lines of ln τ and the reciprocal of the temperature (1/T). The values of the activation energy were accounted for the hopping process at low temperatures, while a thermally activated conduction process was dominant at higher temperatures.The maximum barrier height, W_m, was found to be temperature and frequency dependent for all phthalocyanine compounds. The value W_m depends greatly on the nature of the central atom and electrode material type. The correlated barrier hopping model was found to be the appropriate mechanism to describe the charge carrier's transport in phthalocyanine films.

The continuous progress in thin film materials and devices has greatly promoted the development in the field of flexible electronics. As one of the most common thin film devices, thin film transistors (TFTs) are significant building blocks for flexible platforms. Flexible oxide-based TFTs are well compatible with flexible electronic systems due to low process temperature, high carrier mobility, and good uniformity. The present article is a review of the recent progress and major trends in the field of flexible oxide-based thin film transistors. First, an introduction of flexible electronics and flexible oxide-based thin film transistors is given. Next, we introduce oxide semiconductor materials and various flexible oxide-based TFTs classified by substrate materials including polymer plastics, paper sheets, metal foils, and flexible thin glass. Afterwards, applications of flexible oxide-based TFTs including bendable sensors, memories, circuits, and displays are presented. Finally, we give conclusions and a prospect for possible development trends.

Using the measured capacitance-voltage and current-voltage characteristics of the rectangular AlN/GaN heterostructure field-effect transistors (HFETs) with the side-Ohmic contacts, it was found that the polarization Coulomb field scattering in the AlN/GaN HFETs was greatly weakened after the side-Ohmic contact processing, however, it still could not be ignored. It was also found that, with side-Ohmic contacts, the polarization Coulomb field scattering was much stronger in AlN/GaN HFETs than in AlGaN/AlN/GaN and In_0.17Al_0.83N/AlN/GaN HFETs, which was attributed to the extremely thinner barrier layer and the stronger polarization of the AlN/GaN heterostructure.

The optoelectronic properties of heterojunction thin film devices with ITO/CuPc/C60/Al structure have been investigated by analyzing their current–voltage characteristics, optical absorption and photocurrent. In this organic photovoltaic device, CuPc acts as an optically active layer, C60 as an electron-transporting layer and ITO and Al as electrodes. It is observed that, under illumination, excitons are formed, which subsequently drift towards the interface with C60, where an internal electric field is present. The excitons that reach the interface are subsequently dissociated into free charge carriers due to the electric field present at the interface. The experimental results show that in this device the total current density is a function of injected carriers at the electrode–organic semiconductor surface, the leakage current through the organic layer and collected photogenerated current that results from the effective dissociation of excitons.

Although perovskite solar cells containing methylamine cation can show high power conversion efficiency, stability is a concern. Here, methylamine-free perovskite material Cs_xFA_1–xPbI₃ was synthesized by a one-step method. In addition, we incorporated smaller cadmium ions into mixed perovskite lattice to partially replace Pb ions to address the excessive internal strain in perovskite structure. We have found that the introduction of Cd can improve the crystallinity and the charge carrier lifetime of perovskite films. Consequently, a power conversion efficiency as high as 20.59% was achieved. More importantly, the devices retained 94% of their initial efficiency under 1200 h of continuous illumination.

Two-dimensional (2D) materials with unique properties have received a great deal of attention in recent years. This family of materials has rapidly established themselves as intriguing building blocks for versatile nanoelectronic devices that offer promising potential for use in next generation optoelectronics, such as photodetectors. Furthermore, their optoelectronic performance can be adjusted by varying the number of layers. They have demonstrated excellent light absorption, enabling ultrafast and ultrasensitive detection of light in photodetectors, especially in their single-layer structure. Moreover, due to their atomic thickness, outstanding mechanical flexibility, and large breaking strength, these materials have been of great interest for use in flexible devices and strain engineering. Toward that end, several kinds of photodetectors based on 2D materials have been reported. Here, we present a review of the state-of-the-art in photodetectors based on graphene and other 2D materials, such as the graphene, transition metal dichalcogenides, and so on.

Based on the measured capacitance-voltage (C-V) curves and current-voltage (I-V) curves for the prepared differently-sized AlN/GaN heterostructure field-effect transistors (HFETs), the I-V characteristics of the AlN/GaN HFETs were simulated using the quasi-two-dimensional (quasi-2D) model. By analyzing the variation in the electron mobility for the two-dimensional electron gas (2DEG) with the channel electric field, it is found that the different polarization charge distribution generated by the different channel electric field distribution can result in different polarization Coulomb field (PCF) scattering. The 2DEG electron mobility difference is mostly caused by the PCF scattering which can reach up to 899.6 cm²/(V·s) (sample a), 1307.4 cm²/(V·s) (sample b), 1561.7 cm²/(V·s) (sample c) and 678.1 cm²/(V·s) (sample d), respectively. When the 2DEG sheet density is modulated by the drain-source bias, the electron mobility for samples a, b and c appear to peak with the variation of the 2DEG sheet density, but for sample d, no peak appears and the electron mobility rises with the increase in the 2DEG sheet density.

Silicon photonics is an emerging competitive solution for next-generation scalable data communications in different application areas as high-speed data communication is constrained by electrical interconnects. Optical interconnects based on silicon photonics can be used in intra/inter-chip interconnects, board-to-board interconnects, short-reach communications in datacenters, supercomputers and long-haul optical transmissions. In this paper, we present an overview of recent progress in silicon optoelectronic devices and optoelectronic integrated circuits(OEICs) based on a complementary metal-oxide-semiconductor-compatible process, and focus on our research contributions. The silicon optoelectronic devices and OEICs show good characteristics, which are expected to benefit several application domains, including communication, sensing, computing and nonlinear systems.

The optical properties of polypyrrole (Ppy) thin films upon 2 MeV electron beam irradiation changes with different doses. The induced changes in the optical properties for Ppy thin films were studied in the visible range 300 to 800 nm at room temperature. The optical band gap of the pristine Ppy was found to be 2.19 eV and it decreases up to 1.97 eV for a 50 kGy dose of 2 MeV electron beam. The refractive index dispersion of the samples obeys the single oscillator model. The obtained results suggest that electron beam irradiation changes the optical parameters of Ppy thin films.

Flexible and wearable optoelectronic devices have been developing to a new stage due to their unique capacity for the possibility of a variety of wearable intelligent electronics, including bendable smartphones, foldable touch screens and antennas, paper-like displays, and curved and flexible solid-state lighting devices. Before extensive commercial applications, some issues still have to be solved for flexible and wearable optoelectronic devices. In this regard, this review concludes the newly emerging flexible substrate materials, transparent conductive electrodes, device architectures and light manipulation methods. Examples of these components applied for various kinds of devices are also summarized. Finally, perspectives about the bright future of flexible and wearable electronic devices are proposed.