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Using bilayer graphene structures (L-type and disk-type structures), we numerically demonstrate a tunable single-band terahertz metamaterial absorber with nearly perfect (100%) absorption by continuously adjusting the graphene Fermi energy parameters to determine the maximum absorption rate, the corresponding center frequency, and bandwidth. Graphene distinct dielectric–metal transition properties make it possible to achieve tunable terahertz absorption. The maximum absorption rate increases from 18% to 100% when the Fermi energy is increased from 0.1 to 1 eV. At 1 eV, the absorption rate exceeds 90% in the range of 0.57–1.03 THz. The incident angle is also tested. When the angle is in the range of 60°, excellent adsorption performance is maintained.

Lead iodide, PbI2, is one of the promising metal halide materials used for x- and γ-ray detection; it is also a key constituent of organometallic halide perovskites for low-cost solar cells. Here, we report a mature technology for the fabrication of microelectronic devices—an electron beam evaporation method to prepare highly uniform PbI2 thin films with a size of up to 10 cm × 10 cm on various rigid and flexible substrates at room temperature; the fabricated x-ray detectors show a consistent detection performance. The detection performance of the PbI2 thin film based flexible detectors demonstrate high robustness and stability under various bending states, suggesting themselves as potential candidates for the development of next-generation, large-area, and flexible x-ray detecting devices by using pure PbI2 films.

In this work, we prepared the thermal evaporated amorphous selenium (a-Se) thin films with different evaporation time at low vacuum degree 10-2 Pa. The results showed a-Se thin films were easier to be crystallized with prolonging evaporation time. Also, the transmittance absorption edges of a-Se thin films showed a blue shift with the enhanced optical energy gap from 2.08 eV to 2.15 eV. Further, the dark current was found to depend on energy gap, and became lower as extending evaporation time. Moreover, a-Se thin films showed the improved X-ray photocurrent gain, with a rapid photoresponse and a small applied voltage requirement. Overall, this work revealed that the increase of evaporation time led to better deposition quality of thin films, enhancing energy gap and X-ray photoresponse, but thin films were not able to resist to higher temperature anymore.

Titanium dioxide (TiO2) films have been prepared by DC reaction magnetron sputtering technique on different substrates (glass, SiO2, platinum electrode-Pt, Silicon-Si). X-ray diffraction (XRD) patterns showed that all TiO2 films were grown along the preferred orientation of (110) plane. Samples on Si and Pt substrates are almost monophasic rutile, however, samples on glass and SiO2 substrates accompanied by a weak anatase structure. Atomic force microscopy (AFM) images revealed uniform grain distribution except for films on Pt substrates. Photoluminescence (PL) spectra showed obvious intrinsic emission band, but films on glass was accompanied by a distinct defect luminescence region. Raman spectroscopy suggested that all samples moved to high wavenumbers and films on glass moved obviously.

The performance of dye-sensitized solar cells (DSSC) depends strongly on the electrolyte. In this paper, the electrolytes with various solvents and different potassium iodide (KI) & iodine (I2) concentration were prepared and their influence on the DSSC performance were investigated. The results revealed DSSC with electrolyte prepared by organic solvent show better performance than that of inorganic solvent. Meanwhile, the increasing of KI concentration from 0.1 to 0.6 mol/L can effectively improve the short-circuit current density (Jsc) from 0 2, correspondingly, the DSSC conversion efficiency (η) increased from 0.04% to 0.11%. On the other hand, the Jsc and η of DSSC increased firstly then decreased with the I2 concentration raised from 0.025 mol/L to 0.125 mol/L. It is worth to notice that the open-circuit voltage (Voc) of DSSC is almost unchanged with the concentration of KI and I2. In this paper, the best performance DSSC (Jsc=0.87 mA/cm2, Voc=0.57 mV, η=0.23%) can be obtained with electrolyte at a KI and I2 concentration of 0.6 mol/L and 0.075 mol/L respectively. Finally, the electrolytes used water and mixture of acetonitrile & ethylene glycol as solvents showed the latter presented better stability after setting at room temperature for 72 hours.

The ZnO thin films have been prepared by sol-gel method at different annealing temperatures and aging time. The structural properties of ZnO thin films were investigated by X-ray diffraction (XRD) patterns and atomic force microscope (AFM) images. The results indicated that the film possess a hexagonal wurtzite structure with preferred orientation along the (002) direction. The crystalline quality of films improved with increasing post-annealing temperature, while gradually worsened with prolonging aging time. The optical properties of ZnO thin films were studied by the ultra-violet transmittance (UV-Vis) and photoluminescence (PL) spectra. The variations of UV-Vis transmittance and energy gap accorded well with the tendency presented in XRD patterns and AFM images. The PL spectra appeared the apparent ultraviolet emission and visible emissions. As the annealing temperature increased, the ultraviolet and visible emissions of films enhanced and decreased respectively. However, as the sol aging time prolonged, the PL emission presented an opposite tendency.