In this paper, we have demonstrated two types of polymer waveguide switches with nematic liquid crystal cladding. Although the higher propagation loss in LC materials hinders them from serving as the waveguide film, it has been common that LC exhibiting a large optical anisotropy and an electrically controllable molecular alignment are applied to investigations of slab-waveguide cut off switching as active medium claddings. For this type of switching geometry, a higher contrast ratio is obtainable because simple TE or TM polarized waves may be supported in the planar polymer waveguide.
High-quality perovskite CsPbBr3 quantum dots (QDs-CsPbBr3) were prepared using the ultrasonic oscillation method, which is simple and provides variable yield according to requirements. The emission spectra over a large portion of the visible spectral region (450–650 nm) of QD-CsPbX3 (X = Cl, Br, and I) have tunable compositions that can be halide exchanged using the halide anion exchange technique and quantum size-effects. A strong peak with high intensity of (200) lattice plane of purified QDs-CsPbBr3 film is obtained, confirming the formation of an orthorhombic perovskite crystal structure of the Pnma space group. The photoluminescence of QDs-CsPbBr3 was characterized using a narrow line-width emission of 20 nm, with high quantum yields of up to 99.2%, and radioactive lifetime increasing to 26 ns. Finally, through the excellent advantages of QDs-CsPbBr3 mentioned above, purified perovskite QDs-CsPbBr3 as an active layer was utilized in perovskite quantum dot light-emitting diodes structure applications. As a result, the perovskite QDs-CsPbBr3 light-emitting diodes (LEDs) exhibits a turn-on voltage of 7 V and a maximum luminance of 5.1 cd/m2.
Numerous studies have addressed the use of perovskite materials for fabricating a wide range of optoelectronic devices. This study employs the deposition of an electron transport layer of C60 and an Ag electrode on CH3NH3PbBr3 perovskite crystals to complete a photodetector structure, which exhibits a metal–semiconductor–metal (MSM) type structure. First, CH3NH3PbBr3 perovskite crystals were grown by inverse temperature crystallization (ITC) in a pre-heated circulator oven. This oven was able to supply uniform heat for facilitating the growth of high-quality and large-area crystals. Second, the different growth temperatures for CH3NH3PbBr3 perovskite crystals were investigated. The electrical, optical, and morphological characteristics of the perovskite crystals were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible spectroscopy, and photoluminescence (PL). Finally, the CH3NH3PbBr3 perovskite crystals were observed to form a contact with the Ag/C60 as the photodetector, which revealed a responsivity of 24.5 A/W.
ZnO films with c-axis (0002) orientation have been successfully grown by RF magnetron sputtering on interdigital transducer/Al 2 O 3 /glass substrates. Alumina films were deposited on glass substrates by electron beam evaporation. The crystalline structure and surface roughness of the films were investigated by X-ray diffraction and atomic force microscopy, respectively. The phase velocity and coupling coefficient of surface acoustic wave (SAW) device apparently increased when we increased the thickness of the alumina films. In addition, an excellent temperature coefficient of frequency of the SAW device was obtained by increasing the thickness of the alumina films. This experimental result is beneficial for enhancing the performance of ZnO thin-film SAW devices on inexpensive glass substrates.
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