Co-precipitation synthesis of ZnAl2O4: Cr3+ phosphor for better light penetration in pc-LED

Cr doped ZnAl₂O₄ spinel samples were prepared by the traditional solid state reaction and co-precipitation synthetic route, and the results suggest that the co-precipitation method has some superiority in contrast to the solid state reaction method. XRD, FT-IR, and XPS spectra confirmed that the well-crystallized spinel cubic phase of ZnAl₂O₄: Cr³⁺ samples were successfully formed. The morphology of the samples was investigated by FE-SEM and FE-TEM, and the results show that the samples by the co-precipitation route can generate a smaller size of particles compared to the solid state reaction. Photoluminescence excitation spectra monitored at 686 nm are comprised of two broad excitation bands near 530 nm and 395 nm, and the emission spectra show emissions ranging from 640 to 780 nm, due to the ²E?→?⁴A₂ spin-forbidden transition of Cr³⁺ ions in spinel lattices. The optimized concentration monitored at 686 nm is 1%, while at 693 nm is 3.5%. Compared with the samples by solid state reaction method, the samples by co-precipitation method show preferable luminescent properties, such as the higher photoluminescence intensity and higher quantum efficiency. Several phosphor-converted LEDs were to investigate the applicability of the prepared samples. The results confirm that the phosphor has potential applications in plant growth and supplementing the red region in white-LEDs and the phosphors prepared by co-precipitation are more suitable to be used in phosphor-converted LED devices due to their preferable luminescent properties.

     

Mg gas infiltration for the fabrication of MgB2 pellets using nanosized and microsized B powders

MgB₂ superconductor pellets were synthesized through Mg gas infiltration method using nanosized- and microsized B powders. There was a marked difference in the superconducting properties of the two samples, particularly in the pinning force and dominant pinning mechanism. The microstructures of the samples were observed using HR-TEM and STEM-HAADF, and the results showed that the primary reason for the difference in the superconducting properties is the distribution of the nanosized second-phase particle MgO. Additionally, a feasible reaction model for the Mg gas infiltration method was established. Compared to the Mg liquid infiltration method, the gas infiltration showed better penetrability ability with a small amount of residual Mg. This study presents a novel synthesis process to fabricate an MgB₂ pellet with superior density and superconducting properties. This method can be used in multiple applications such as superconducting bearings, compact superconductor magnets, and magnetic shielding.     

TiI4-doping induced bulk defects passivation in halide perovskites for high efficient photovoltaic devices

Power conversion efficiency (PCE) and stability are two important properties of perovskite solar cells (PSCs). Particularly, defects in the perovskite films could cause the generation of trap states, thereby increasing the nonradiative recombination. To address this issue, suitable dopants can be incorporated to react with non-bonded atoms or surface dangling bonds to passivate the defects. Herein, we introduced TiI₄ into CH₃NH₃PbI₃ (MAPbI₃) film and obtained a dense and uniform morphology with large crystal grains and low defect density. The champion cell based on 0.5% TiI₄-doped MAPbI₃ achieved a PCE as high as 20.55%, which is superior to those based on pristine MAPbI₃ (17.64%). Moreover, the optimal solar cell showed remarkable stability without encapsulation. It retained 88.03% of its initial PCE after 300 h of storage in ambient. This work demonstrates TiI₄ as a new and effective passivator for MAPbI₃ film.     

Improving the fill factor of N2200-based all polymer solar cells by introducing EPPDI as a solid additive

A cheap and commercially available small molecule (namely EPPDI) is introduced to the active layer of N2200-based all polymer solar cells as a solid additive. EPPDI at the optimal ratio can improve the D-A nano-scale morphology and reduce trap density of the active layer by filling morphological spaces. As a result, the photovoltaic performance of the resulting devices based on PF2:N2200 are increased from 6.28% to 7.03% with significantly enhanced fill factor. This work demonstrates a facile approach for improving the performance of all polymer solar cells.     

Lewis acid-oxygen vacancy interfacial synergistic catalysis over SO42−/Ce0.84Zr0.16O2–WO3–ZrO2 for N,N-diethylation of aniline with ethanol

Herein, a new mechanism involving Lewis acid-oxygen vacancy interfacial synergistic catalysis for aniline N,N-diethylation with ethanol was proposed, and the SO₄²⁻/Ce_0.84Zr_0.16O₂–WO₃–ZrO₂ catalyst (SCWZ) with both Lewis acid sites and oxygen vacancies was synthesized by the hydrothermal method, which shows better catalytic activity than the reported solid acidic catalysts. Besides, the SO₄²⁻/ZrO₂ (SZ) and SO₄²⁻/WO₃–ZrO₂ (SWZ) catalysts were also prepared and compared with SCWZ to investigate the synergistic effect of each component. The SO₄²⁻ and WO₃ mainly generate Lewis acid by bonding with ZrO₂, which is beneficial for the fracture of the N–H bond in aniline. The Ce_0.84Zr_0.16O₂ solid solution mainly plays a vital role in generating the oxygen vacancies as the interface active species, which can participate in stripping –OH from ethanol, then the carbocation will also be released, which only needs 1.3805 kcal/mol energy, calculated by density functional theory (DFT), to be input. In comparison, the traditional reaction mechanism needs the Brønsted acidic sites to promote the protonation of ethanol, then dehydration and subsequent formation of carbocation followed, and 108.6846 kcal/mol energy needs to be input, which is far higher than that of the new mechanism. The apparent activation energy (E_a) over SCWZ was measured by experiment to be 34.09 kJ/mol, which is much lower than that of SWZ (47.10 kJ/mol) and SZ (54.37 kJ/mol), illustrating comparatively preferable kinetics for SCWZ than that of SWZ and SZ. Besides, the conversion of aniline and selectivity to N,N-diethylaniline over SCWZ reach almost 100% and 73%, respectively. The SCWZ can be renewed for 4 times without rapid deactivation, and the longevity of SCWZ is longer than that of SWZ and SZ, as the loaded SO₄²⁻ and tetragonal ZrO₂ are stabilized by Ce_0.84Zr_0.16O₂ and WO₃, respectively.     

Evolution of linear edge dislocation in atmospheric turbulence and free space

In accordance with the extended Huygens–Fresnel principle, the evolution of linear edge dislocation propagating through atmospheric turbulence is studied, and the effects of waist width and the slope of linear edge dislocation are investigated. It is shown that when linear edge dislocation beams propagate through atmospheric turbulence, if the waist width is not equal and the slope is not zero, then the linear edge dislocation vanishes and transforms into an optical vortex with a topological charge of ?1 or +1. The optical vortex and an optical vortex that is created annihilate when the transmission distance is far enough. The linear edge dislocation vanishes when the slope is zero. If the waist width is equal, then the linear edge dislocation will vanish regardless of the slope value. For linear edge dislocation beams in free space, when selecting specific parameters, linear edge dislocation always exists.     

Synthesis of SnO2@MnO2@graphite nanosheet with high reversibility and stable structure as a high-performance anode material for lithium-ion batteries

In this study, SnO₂@MnO₂@graphite (SMG) anode material is prepared via a facile ball-milling approach combined with hydrothermal treatment. SnO₂ and MnO₂ nanoparticles are evenly dispersed on numerous sheet-like graphite. MnO₂ can not only play a catalytic role for facilitating the conversion reaction of Sn/Li₂O to SnO₂, but also as a barrier to impede the coarsening of Sn in the composite. Meanwhile, graphite nanosheets could serve as an ideal volume expansion buffer and good electron conductor. Consequently, the SMG anode delivers superior reversible capacity of 1048.5 mAhg⁻¹, ideal rate capability of 522.2 mAhg⁻¹ at 5.0 A g^-1 and stable long-life cyclic performance of 814.8 mAhg⁻¹ at 1.0 A g^-1 after 1000 cycles. This result indicates that the incorporation of MnO₂, graphite nanosheet and SnO₂ have a great potential in enhancing the performance of SnO₂-based anode for battery applications.     

Investigation on the mechanism of charge generation in organic heterojunctions: Analysis of I–V and C–V characteristics

The charge generation mechanism of organic heterojunction (OHJ) consisted of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) and different hole transporting materials (HTMs) are studied systematically by current-voltage (I–V) and capacitance-voltage measurements. The analysis of I–V characteristics of the devices based on OHJs at forward and reverse voltages by comparing the thickness of HTM layers finds that a forward and reverse symmetrical I–V curve is observed at thin HTM layers and the forward current becomes larger than the reverse current with the increase of HTM thickness, fully illustrating the effectiveness of OHJ charge generation. Moreover, the I–V characteristics at different temperatures indicate that the efficient charge generation is originated from electron tunneling rather than diffusion. And the C–V and capacitance-frequency (C–F)characteristics further illustrate the highly efficient charge generation ability of OHJs so that the charge density is as high as 4.5 × 10¹⁷ cm⁻³, guaranteeing the high conductivity of OHJs, which is very beneficial to developing highly efficient OLEDs using OHJs as charge injector and generator.     

Optimal 5G network slicing using machine learning and deep learning concepts

Network slicing is predetermined to hold up the diversity of emerging applications with enhanced performance and flexibility requirements in the way of splitting the physical network into numerous logical networks. Consequently, a tremendous data count has been generated with an enormous number of mobile phones due to these applications. This has made remarkable challenges and has a considerable influence on the network slicing performance. This work aims to design an efficient network slicing using a hybrid learning algorithm. Thus, we proposed a model, which involves three main phases: (a) Data collection, (b) Optimal weighted feature extraction (OWFE), and (c) Slicing classification. First, we collected the 5G network slicing dataset, which involves the attributes associated with various network devices like “user device type, duration, packet loss ratio, packet delay budget, bandwidth, delay rate, speed, jitter, and modulation type.” Next, we performed the OWFE, in which a weight function is multiplied with the attribute values to have high scale variation. We optimized this weight function by the hybridization of two meta-heuristic algorithms—glowworm swarm optimization and deer hunting optimization algorithm (DHOA)—and named the proposed model glowworm swarm-based DHOA (GS-DHOA). For the given attributes, we classified the exact network slices like “eMBB, mMTC, and URLLC” for each device by a hybrid classifier using deep belief and neural networks. The weight function of both networks is optimized by the GS-DHOA. The experiment results revealed that the proposed model could influence the provision of accurate 5G network slicing.