Mechanism and Growth of Flexible ZnO Nanostructure Arrays in a Facile Controlled Way

Nanostructure arrays-based flexible devices have revolutionary impacts on the application of traditional semiconductor devices. Here, a one-step method to synthesize flexible ZnO nanostructure arrays on Zn-plated flexible substrate in Zn(NO3)2/NH3⋅H2O solution system at 70–90∘C was developed. We found out that the decomposition of Zn(OH)2 precipitations, formed in lower NH3⋅H2O concentration, in the bulk solution facilitates the formation of flower-like structure. In higher temperature, 90∘C, ZnO nanoplate arrays were synthesized by the hydrolysis of zinc hydroxide. Highly dense ZnO nanoparticale layer formed by the reaction of NH3⋅H2O with Zn plating layer in the initial self-seed process could improve the vertical alignment of the nanowires arrays. The diameter of ZnO nanowire arrays, from 200 nm to 60 nm, could be effectively controlled by changing the stability of Zn(NH3)42+ complex ions by varying the ratio of Zn(NO3)2 to NH3⋅H2O which further influence the release rate of Zn2+ ions. This is also conformed by different amounts of the Zn vacancy as determined by different UV emissions of the PL spectra in the range of 380–403 nm

A Lightweight Object Detection Network for Real-Time Detection of Driver Handheld Call on Embedded Devices

It is necessary to improve the performance of the object detection algorithm in resource-constrained embedded devices by lightweight improvement. In order to further improve the recognition accuracy of the algorithm for small target objects, this paper integrates 5 × 5 deep detachable convolution kernel on the basis of MobileNetV2-SSDLite model, extracts features of two special convolutional layers in addition to detecting the target, and designs a new lightweight object detection network—Lightweight Microscopic Detection Network (LMS-DN). The network can be implemented on embedded devices such as NVIDIA Jetson TX2. The experimental results show that LMS-DN only needs fewer parameters and calculation costs to obtain higher identification accuracy and stronger anti-interference than other popular object detection models

Driver Distraction Detection Method Based on Continuous Head Pose Estimation

In view of the fact that the detection of driver’s distraction is a burning issue, this study chooses the driver’s head pose as the evaluation parameter for driving distraction and proposes a driver distraction method based on the head pose. The effects of single regression and classification combined with regression are compared in terms of accuracy, and four kinds of classical networks are improved and trained using 300W-LP and AFLW datasets. The HPE_Resnet50 with the best accuracy is selected as the head pose estimator and applied to the ten-category distracted driving dataset SF3D to obtain 20,000 sets of head pose data. The differences between classes are discussed qualitatively and quantitatively. The analysis of variance shows that there is a statistically significant difference in head posture between safe driving and all kinds of distracted driving at 95% and 90% confidence levels, and the postures of all kinds of driving movements are distributed in a specific Euler angle range, which provides a characteristic basis for the design of subsequent recognition methods. In addition, according to the continuity of human movement, this paper also selects 90 drivers’ videos to analyze the difference in head pose between safe driving and distracted driving frame by frame. By calculating the spatial distance and sample statistics, the results provide the reference point, spatial range, and threshold of safe driving under this driving condition. Experimental results show that the average error of HPE_Resnet50 in AFLW2000 is 6.17° and that there is an average difference of 12.4° to 54.9° in the Euler angle between safe driving and nine kinds of distracted driving on SF3D

Conduction Band Fine Structure in Colloidal HgTe Quantum Dots

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Conformal Fabrication of Colloidal Quantum Dot Solids for Optically Enhanced Photovoltaics

Colloidal quantum dots (CQD) are an attractive thin-film material for photovoltaic applications due to low material costs, ease of fabrication, and size-tunable band gap. Unfortunately, today they suffer from a compromise between light absorption and photocarrier extraction, a fact that currently prevents the complete harvest of incoming above-band-gap solar photons. We have investigated the use of structured substrates and/or electrodes to increase the effective light path through the active material and found that these designs require highly conformal application of the light-absorbing films to achieve the greatest enhancement. This conformality requirement derives from the need for maximal absorption enhancement combined with shortest-distance charge transport. Here we report on a means of processing highly conformal layer-by-layer deposited CQD absorber films onto microstructured, light-recycling electrodes. Specifically, we engineer surface hydrophilicity to achieve conformal deposition of upper layers atop underlying ones. We show that only with the application of conformal coating can we achieve optimal quantum efficiency and enhanced power conversion efficiency in structured-electrode CQD cells

Hybrid Colloidal Stabilization Mechanism toward Improved Photoluminescence and Stability of CdSe/CdS Core/Shell Quantum Dots

Colloidal quantum dots can be stabilized in either a polar solvent or a nonpolar solvent depending on their surface chemistry. The former is typically achieved by charge stabilization while the latter by steric hindrance. This allows reversible tuning of their surface polarity for targeted application by engineering their ligand profile. Here we developed a hybrid stabilization approach that leveraged a combination of steric hindrance and charge stabilization simultaneously. We demonstrated this mechanism in a phase transfer process where hexane dispersed and hydrophobic CdSe/CdS core/shell quantum dots were exchanged into the hydrophilic dimethylformamide (DMF) phase. This was achieved by employing both Z-type cadmium acetate and X-type halide ligands. The results suggested only by using this hybrid stabilization strategy were we able to achieve good colloidal stability while preserving their photoluminescence quantum yield. This hybrid ligand strategy may promise new opportunities for the application of QDs in optoelectronic areas

Self-Assembled PbSe Nanowire:Perovskite Hybrids

Inorganic semiconductor nanowires are of interest in nano- and microscale photonic and electronic applications. Here we report the formation of PbSe nanowires based on directional quantum dot alignment and fusion regulated by hybrid organic–inorganic perovskite surface ligands. All material synthesis is carried out at mild temperatures. Passivation of PbSe quantum dots was achieved via a new perovskite ligand exchange. Subsequent <i>in situ</i> ammonium/amine substitution by butylamine enables quantum dots to be capped by butylammonium lead iodide, and this further drives the formation of a PbSe nanowire superlattice in a two-dimensional (2D) perovskite matrix. The average spacing between two adjacent nanowires agrees well with the thickness of single atomic layer of 2D perovskite, consistent with the formation of a new self-assembled semiconductor nanowire:perovskite heterocrystal hybrid