Study of Atomic Oxygen Airglow Intensities and Air Temperature near Mesopause Obtained by Ground-Based and Satellite Instruments above Baikal Natural Territory

The research studied the comparison of the night air temperatures and the atomic oxygen airglow intensities at the mesopause obtained with satellite and ground-based instruments. Satellite data used in this study were obtained with the SABER limb-scanning radiometer operating aboard the TIMED satellite. Data of ground-based monitoring were obtained using the KEO Scientific “Arinae” Fabry–Pérot interferometer adapted for aeronomic research. Since an interferometer detects parameters of the 557.7 nm line for the entire emission layer, it is not quite appropriate to perform a direct comparison between the upper atmospheric temperature obtained from ground-based observations and that from a satellite at a particular height. To compare temperatures correctly, the effective temperature must be calculated based on satellite data. The effective temperature is a height-averaged temperature profile with the weight factors equal to the 557.7 nm line intensity at relevant heights. The height profile of intensity of this natural green airglow of the upper atmosphere is calculated from the height profile of atomic oxygen concentration. Data on chemical composition and air temperature at the mesopause from SABER were used to calculate the profiles. The night intensity of the 557.7 nm emission obtained from satellite data in this way was in good accordance with the results of ground-based observations, but the temperatures were different. The reason for temperature discrepancy was assumed to lie in the incorrect position of the intensity maximum of the reconstructed emission layer. According to our calculations based on SABER data, the intensity peak was observed at the height of 94–95 km. By shifting it relative to the SABER temperature height profile, we re-calculated the effective temperatures and compared them with the interferometer data. The best coincidence between seasonal temperature variations obtained using the proposed method was achieved when the maximum of the reconstructed 557.7 nm intensity height profile was shifted to 97 km, but it could not eliminate minor local differences in temperature behavior.

The Design of the Emission Layer for Electron Multipliers

The electron multipliers gain is closely related to the secondary electron emission coefficient (SEE) of the emission layer materials. The SEE is closely related to the thickness of the emission layer. If the emission layer is thin, the low SEE causes the low gain of electron multipliers. If the emission layer is thick, the conductive layer can't timely supplement charge to the emission layer, the electronic amplifier gain is low too. The electron multipliers usually choose Al2O3 and MgO film as the emission layer because of the high SEE level. MgO easy deliquescence into Mg(OH)2 Mg2(OH)2CO3 and MgCO3 resulting in the lower SEE level. The SEE level of Al2O3 is lower than MgO, but Al2O3 is stable. We designed a spherical system for testing the SEE level of materials, and proposed to use low-energy secondary electrons instead of low-energy electron beam for neutralization to measuring the SEE level of Al2O3, MgO, MgO/Al2O3, Al2O3/MgO, and precisely control the film thickness by using atomic layer deposition. We propose to compare the SEE under the adjacent incident electrons energy to partition the SEE value of the material, and obtain four empirical formulas for the relationship between SEE and thickness. Since the main materials that cause the decrease in SEE are Mg2(OH)2CO3 and MgCO3, we use the C element atomic concentration measured by XPS to study the deliquescent depth of the material. We propose to use the concept of transition layer for SEE interpretation of multilayer materials. Through experiments and calculations, we put forward a new emission layer for electron multipliers, including 2–3 nm Al2O3 buffer layer, 5–9 nm MgO main-body layer, 1 nm Al2O3 protective layer or 0.3 nm Al2O3 enhancement layer. We prepared this emission layer to microchannel plate (MCP), which significantly improved the gain of MCP. We can also apply this new emission layer to channel electron multiplier and separate electron multiplier.

A case study of a ducted gravity wave event over northern Germany using simultaneous airglow imaging and wind-field observations

An intriguing and rare gravity wave event was recorded on the night of 25 April 2017 using a multi-wavelength all-sky airglow imager over northern Germany. The airglow imaging observations at multiple altitudes in the mesosphere and lower thermosphere region reveal that a prominent upward propagating wave structure appeared in O(1S) and O2 airglow images. However, the same wave structure was observed to be very faint in OH airglow images, despite OH being usually one of the brightest airglow emissions. In order to investigate this rare phenomenon, the altitude profile of the vertical wavenumber was derived based on collocated meteor radar wind-field and SABER temperature profiles close to the event location. The results indicate the presence of a thermal duct layer in the altitude range of 85–91 km in the south-west region of Kühlungsborn, Germany. Utilizing these instrumental datasets, we present an evidence to show how a leaky duct layer partially inhibited the wave progression in the OH airglow emission layer. The coincidental appearance of this duct layer caused the wave amplitudes to diminish, resulting to exhibit as the faint wave front in the OH airglow images during the course of the night over northern Germany.

Color Tuning of 2-Color Based White Organic Light-Emitting Diodes with Undoped Ultra-Thin Emission Layer

In the research of organic light-emitting diodes (OLEDs), the OLEDs that are fabricated via conventional doping methods have complicated structures and fabrication processes. To overcome these limitations, the ultra-thin emission layer (EML) method, which adopts a simple structure has been effectively used in the research of OLEDs. However, studies on white color OLEDs (WOLEDs) fabricated using the ultra-thin EML method are scarce. In this paper, we report the results of color tuning for the realization of WOLEDs based on an ultra-thin EML structure. The WOLEDs were fabricated and evaluated based on a two-color dopant system (sky-blue dopant and yellow dopant). The fabricated WOLEDs exhibited color coordinates of the International Commission on Illumination (CIE) 1931 from (0.287, 0.436) to (0.486, 0.483) according to the thickness ratio of the two dopants. This result suggests that the WOLEDs color tuned with multi-color dopants can be fabricated based on the ultra-thin EML method, and the development of WOLEDs with high efficiency and stability can be attained in the future.

Effect of Optical and Morphological Control of Single-Structured LEC Device

We investigated the performance of single-structured light-emitting electrochemical cell (LEC) devices with Ru(bpy)3(PF6)2 polymer composite as an emission layer by controlling thickness and heat treatment. When the thickness was smaller than 120–150 nm, the device performance decreased because of the low optical properties and non-dense surface properties. On the other hand, when the thickness was over than 150 nm, the device had too high surface roughness, resulting in high-efficiency roll-off and poor device stability. With 150 nm thickness, the absorbance increased, and the surface roughness was low and dense, resulting in increased device characteristics and better stability. The heat treatment effect further improved the surface properties, thus improving the device characteristics. In particular, the external quantum efficiency (EQE) reduction rate was shallow at 100 °C, which indicates that the LEC device has stable operating characteristics. The LEC device exhibited a maximum luminance of 3532 cd/m2 and an EQE of 1.14% under 150 nm thickness and 100 °C heat treatment.

Application of quinoline derivatives in third-generation photovoltaics

Among many chemical compounds synthesized for third-generation photovoltaic applications, quinoline derivatives have recently gained popularity. This work reviews the latest developments in the quinoline derivatives (metal complexes) for applications in the photovoltaic cells. Their properties for photovoltaic applications are detailed: absorption spectra, energy levels, and other achievements presented by the authors. We have also outlined various methods for testing the compounds for application. Finally, we present the implementation of quinoline derivatives in photovoltaic cells. Their architecture and design are described, and also, the performance for polymer solar cells and dye-synthesized solar cells was highlighted. We have described their performance and characteristics. We have also pointed out other, non-photovoltaic applications for quinoline derivatives. It has been demonstrated and described that quinoline derivatives are good materials for the emission layer of organic light-emitting diodes (OLEDs) and are also used in transistors. The compounds are also being considered as materials for biomedical applications.

Evolvement Investigation of Secondary Electron Emission for Ultrathin MgO Coatings Prepared by Atomic Layer Deposition

MgO is a kind of high secondary electron yield (SEY) material with important applications in electron multipliers. MgO coatings can be used as the electron emission layer for multiplier dynode to improve the electron gain significantly. However, the SEY investigation on ultrathin MgO coatings is not complete and needed to be supplemented urgently. In this work, a series of MgO coatings with increasing thickness were prepared by atomic layer deposition. SEY properties and energy spectra were characterized, and the effect of coating thickness on SEY was systematically analyzed. Experimental results show that SEY of MgO/Si samples rises as the coating thickness increases. Merely, SEY almost does not change with the coating thickness when the thickness exceeds 30 nm. Then, a SEY semi-empirical theory was employed to interpret the SEY regularities of MgO coatings by regarding the coating samples as ideal double-layer structures. Theoretical calculation quantitatively explained the SEY variation observed during the experiments, and further quantified the SEY contribution level of top coating and bottom substrate for the 1 nm and 20 nm MgO coatings. The work is of great significance for comprehending the SEY of ultrathin MgO coatings and expanding the applications of nanoscale coatings with high SEY.

Light Extraction Efficiency Analysis of Phosphorescent OLED Device with Microlens Array on the Glass Substrate

The Computational simulation is based on the desired packing type of microlens array, either hexagonal or rectangular, onto the planar dual scheme OLED device's light-emitting surface. Both active layers here acted as a phosphorescent emission layer studied to improve device efficiency. The microlens array (MLAs) with hexagonal packing can increase the external quantum efficiency by 35%, which is more than the literature mentioned earlier. It significantly enhances the outcoupling efficiency below the critical angle observation concerning the substrate surface normal. Besides, a broad spectrum is observed with a slight shoulder band around 650 nm in the E.L. (Electroluminance) emission curve. From the CIE x and CIE y index studied, the OLED device connected with either hexagonal or rectangular microlens arrays are more sensitive than the OLED device without microlens arrays to the viewing angle range. The effect of outcoupled efficiency as a function of ETL-TPBi thickness is studied under different polarization modes. Hence, the study suggested that a microlens array with a hexagonal or rectangular packing type on the OLED device's top significantly enhanced light extraction efficiency and provided better device fabrication results.

Novel D-A-D Fluorescent Dyes Based on 9-(p-Tolyl)-2,3,4,4a,9,9a-Hexahydro-1H-Carbazole as a Donor Unit for Solution-Processed Organic Light-Emitting-Diodes

New fluorescent D-A-D dyes containing 9-(p-tolyl)-2,3,4,4a,9,9a-hexahydro-1H-carbazole as a donor unit and 2,1,3-benzochalcogenadiazoles as an electron-withdrawing group were synthesized. The photoluminescent and electroluminescent properties of novel dyes for fluorescent OLED application were investigated. It was demonstrated that the replacement of lightweight heteroatoms by heavier ones enables the fine tuning of the maximum emission without significantly reducing the luminescence quantum yield. The maximum quantum yield value of 62.6% for derivatives based on 2,1,3-benzoxadiazole (1a) in cyclohexane was achieved. Two devices with the architecture of glass/ITO/PEDOT-PSS/poly-TPD/EML/TPBi/LiF/Al (EML = emitting layer) were fabricated to check the suitability of the synthesized compounds as a single active emission layer in OLED. These OLEDs exhibited clear red electroluminescence of the dyes with the maximum current efficiency of 0.85 Cd/A.