Graded 2D/3D Perovskite Hetero-Structured Films with Suppressed Interfacial Recombination for Efficient and Stable Solar Cells via DABr Treatment.

Several strategies and approaches have been reported for improving the resilience and optoelectronic properties of perovskite films. However, fabricating a desirable and stable perovskite absorber layer is still a great challenge due to the optoelectronic and fabrication limitations of the materials. Here, we introduce diethylammonium bromide (DABr) as a post-treatment material for the pre-deposited methylammonium lead iodide (MAPbI3) film to fabricate a high-quality two-dimensional/three-dimensional (2D/3D) stacked hetero-structure perovskite film. The post-treatment method of DABr not only induces the small crystals of MAPbI3 perovskite secondary growth into a large crystal, but also forms a 2D capping layer on the surface of the 3D MAPbI3 film. Meanwhile, the grains and crystallization of 3D film with DABr post-treatment are significantly improved, and the surface defect density is remarkably reduced, which in turn effectively suppressed the charge recombination in the interface between the perovskite layer and the charge transport layer. The perovskite solar cell based on the DABr-treatment exhibited a significantly enhanced power conversion efficiency (PCE) of 19.10% with a notable improvement in the open circuit voltage (VOC) of 1.06 V and good stability, advocating the potential of this perovskite post-treatment approach.

Simultaneous Interfacial Modification and Defect Passivation for Wide-Bandgap Semitransparent Perovskite Solar Cells with 14.4% Power Conversion Efficiency and 38% Average Visible Transmittance.

Perovskite materials offer a great potential in the application of semitransparent solar cells, owing to the tunable bandgap, ease of preparation and excellent photovoltaic property. A majority of works exhibit high average visible-light transmittance (AVT) for semitransparent perovskite solar cells (ST-PSCs) through decreasing perovskite thickness, leading to sacrificing the power conversion efficiency (PCE) of the device. Herein, a wide-bandgap (WBG) perovskite of Cs0.2 FA0.8 Pb(I0.6 Br0.4 )3 is applied as absorber in ST-PSCs, which is a tremendous progress to balance both large PCE and high AVT. Moreover, a strategy of simultaneous interfacial modification and defect passivation is provided to enhance the performance of WBG ST-PSCs. Consequently, an inverted planar structure WBG perovskite solar cell (PSC) achieves 15.06% of PCE with excellent stability by restraining the interfacial energy loss and suppressing the nonradiative recombination. Furthermore, the ST-PSC obtains high PCE of 14.40% with an AVT of 38% by means of optimizing the transparent electrode. This work provides an efficient and simple method to improve the performance and AVT of ST-PSCs for the application in building-integrated photovoltaics.

A Modified Sequential Deposition Route for High-Performance Carbon-Based Perovskite Solar Cells under Atmosphere Condition.

Carbon-based hole transport material (HTM)-free perovskite solar cells have exhibited a promising commercialization prospect, attributed to their outstanding stability and low manufacturing cost. However, the serious charge recombination at the interface of the carbon counter electrode and titanium dioxide (TiO2) suppresses the improvement in the carbon-based perovskite solar cells' performance. Here, we propose a modified sequential deposition process in air, which introduces a mixed solvent to improve the morphology of lead iodide (PbI2) film. Combined with ethanol treatment, the preferred crystallization orientation of the PbI2 film is generated. This new deposition strategy can prepare a thick and compact methylammonium lead halide (MAPbI3) film under high-humidity conditions, which acts as a natural active layer that separates the carbon counter electrode and TiO2. Meanwhile, the modified sequential deposition method provides a simple way to facilitate the conversion of the ultrathick PbI2 capping layer to MAPbI3, as the light absorption layer. By adjusting the thickness of the MAPbI3 capping layer, we achieved a power conversation efficiency (PCE) of 12.5% for the carbon-based perovskite solar cells.

Photoinduced-reset and multilevel storage transistor memories based on antimony-doped tin oxide nanoparticles floating gate.

Recently, antimony-doped tin oxide nanoparticles (ATO NPs) have been widely used in the fields of electronics, photonics, photovoltaics, sensing, and other fields because of their good conductivity, easy synthesis, excellent chemical stability, high mechanical strength, good dispersion and low cost. Herein, for the first time, a novel nonvolatile transistor memory device is fabricated using ATO NPs as charge trapping sites to enhance the memory performance. The resulting organic nano-floating gate memory (NFGM) device exhibits outstanding memory properties, including tremendous memory window (∼85 V), superhigh memory on/off ratio (∼109), long data retention (over 10 years) and eminent multilevel storage behavior, which are among the optimal performances in NFGM devices based on organic field effect transistors. Additionally, the device displays photoinduced-reset characteristic with low energy consumption erasing operation. This study provides novel avenues for the manufacture of simple and low-cost data storage devices with outstanding memory performance, multilevel storage behavior and suitability as platforms for integrated circuits.

Preparation of Fluorescent Dye-Doped Biocompatible Nanoparticles for Cell Labeling.

In this paper, we report a series of fluorescent biocompatible nanoparticles (NPs), prepared by a facile reprecipitation-encapsulation method, for cellular labeling. The as-prepared NPs exhibit a narrow size distribution of 70-110 nm, and a core-shell structure comprised of a hybrid core doped with different dyes and a poly-L-lysine (PLL) shell. With coumarin 6, nile red, and meso- tetraphenylporphyrin as the imaging agents, the fluorescent NPs gave green, orange, and red emissions respectively. Due to the positively charged PLL shell, the fluorescent NPs exhibit neglected cytotoxicity and efficient cellular uptake. After incubation with living cells, the results obtained by laser confocal microscope from green, orange, and red channels all clearly show that the fluores- cent NPs are inhomogenously localized inside the cytoplasm without penetrating into the nucleus. Since such PLL-modified NPs can encapsulate other hydrophobic dyes, a wide spectrum of nanoimaging agents is thus expected. Furthermore, the surface amino groups on the PLL shell afford an anchoring site for further bioconjugation, and targeted imaging is also very promising.

In Situ Vanadium Modification Induced a Back Interfacial Field Passivation Effect toward Efficient Kesterite Solar Cells beyond 11% Efficiency.

Realization of a high-quality back electrode interface (BEI) with suppressed recombination is crucial for Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. To achieve this goal, the construction of a traditional chemical passivation effect has been widely adopted and investigated. However, there is currently a lack of reports concerning the construction of a field passivation effect (FPE) for the BEI. Herein, considering the characteristic of the negligible difference in ionic radius between Mo (0.65 Å) and V (0.64 Å) as well as the presence of one less valence electron compared to Mo, vanadium (V) was employed and in situ incorporated into the MoSe2 interfacial layer during the deposition of the Mo:V electrode and selenization process. This allowed for the establishment of a desirable in situ VI-FPE interface with p-MoSe2:V/p-CZTSSe at the BEI. The p-type characteristic in MoSe2:V is attributed to the presence of the VMo acceptor; notably, the Fermi energy level of MoSe2:V has shifted downward by 0.62 eV compared to MoSe2, thereby facilitating the formation of an optimized band alignment between MoSe2:V and the absorber. Consequently, the photovoltaic parameters of the cell-FPE have experienced a significant increase due to the enhanced carrier transportation efficiency compared to cell-ref, resulting in a remarkable improvement in efficiency from 8.28 to 11.11%.

Depression and Internet Gaming Disorder among Chinese Adolescents: A Longitudinal Moderated Mediation Model.

Internet gaming disorder (IGD) is significantly associated with depression across previous studies, and significantly affects the development of mental health among Chinese adolescents. In this two-wave longitudinal research, we tested the mediating role of maladaptive cognition and the moderating role of mindfulness in the linkage between depression and IGD among Chinese adolescents (N = 580, 355 females, average age = 15.76 years, SD = 1.31) who completed questionnaires. Results of regression-based analyses showed that depression was positively related to IGD. Maladaptive cognition significantly mediated the link between depression and IGD. Moreover, mindfulness moderated the second part of the mediation process. Specifically, as the level of mindfulness increased, the influence of depression on the future IGD through maladaptive cognition was weakened. The present study demonstrates the key roles of maladaptive cognition and mindfulness in the link between depression and IGD, and further supports the cognitive-behavioral model of pathological Internet use.

RelativeNAS: Relative Neural Architecture Search via Slow-Fast Learning.

Despite the remarkable successes of convolutional neural networks (CNNs) in computer vision, it is time-consuming and error-prone to manually design a CNN. Among various neural architecture search (NAS) methods that are motivated to automate designs of high-performance CNNs, the differentiable NAS and population-based NAS are attracting increasing interests due to their unique characters. To benefit from the merits while overcoming the deficiencies of both, this work proposes a novel NAS method, RelativeNAS. As the key to efficient search, RelativeNAS performs joint learning between fast learners (i.e., decoded networks with relatively lower loss value) and slow learners in a pairwise manner. Moreover, since RelativeNAS only requires low-fidelity performance estimation to distinguish each pair of fast learner and slow learner, it saves certain computation costs for training the candidate architectures. The proposed RelativeNAS brings several unique advantages: 1) it achieves state-of-the-art performances on ImageNet with top-1 error rate of 24.88%, that is, outperforming DARTS and AmoebaNet-B by 1.82% and 1.12%, respectively; 2) it spends only 9 h with a single 1080Ti GPU to obtain the discovered cells, that is, 3.75× and 7875× faster than DARTS and AmoebaNet, respectively; and 3) it provides that the discovered cells obtained on CIFAR-10 can be directly transferred to object detection, semantic segmentation, and keypoint detection, yielding competitive results of 73.1% mAP on PASCAL VOC, 78.7% mIoU on Cityscapes, and 68.5% AP on MSCOCO, respectively. The implementation of RelativeNAS is available at https://github.com/EMI-Group/RelativeNAS.

GAMMA challenge: Glaucoma grAding from Multi-Modality imAges.

Glaucoma is a chronic neuro-degenerative condition that is one of the world's leading causes of irreversible but preventable blindness. The blindness is generally caused by the lack of timely detection and treatment. Early screening is thus essential for early treatment to preserve vision and maintain life quality. Colour fundus photography and Optical Coherence Tomography (OCT) are the two most cost-effective tools for glaucoma screening. Both imaging modalities have prominent biomarkers to indicate glaucoma suspects, such as the vertical cup-to-disc ratio (vCDR) on fundus images and retinal nerve fiber layer (RNFL) thickness on OCT volume. In clinical practice, it is often recommended to take both of the screenings for a more accurate and reliable diagnosis. However, although numerous algorithms are proposed based on fundus images or OCT volumes for the automated glaucoma detection, there are few methods that leverage both of the modalities to achieve the target. To fulfil the research gap, we set up the Glaucoma grAding from Multi-Modality imAges (GAMMA) Challenge to encourage the development of fundus & OCT-based glaucoma grading. The primary task of the challenge is to grade glaucoma from both the 2D fundus images and 3D OCT scanning volumes. As part of GAMMA, we have publicly released a glaucoma annotated dataset with both 2D fundus colour photography and 3D OCT volumes, which is the first multi-modality dataset for machine learning based glaucoma grading. In addition, an evaluation framework is also established to evaluate the performance of the submitted methods. During the challenge, 1272 results were submitted, and finally, ten best performing teams were selected for the final stage. We analyse their results and summarize their methods in the paper. Since all the teams submitted their source code in the challenge, we conducted a detailed ablation study to verify the effectiveness of the particular modules proposed. Finally, we identify the proposed techniques and strategies that could be of practical value for the clinical diagnosis of glaucoma. As the first in-depth study of fundus & OCT multi-modality glaucoma grading, we believe the GAMMA Challenge will serve as an essential guideline and benchmark for future research.

Rapamycin inhibits the progression of human acute myeloid leukemia by regulating the circ_0094100/miR-217/ATP1B1 axis.

Rapamycin has been reported to inhibit the progression of diverse tumor cells. However, little is known about the functions of rapamycin in acute myeloid leukemia (AML). A Cell Counting Kit-8 (CCK-8) assay was conducted to evaluate cell viability. Flow cytometry analysis was employed to analyze cell apoptosis and cell cycle process. Quantitative real-time polymerase chain reaction (qRT-PCR) assay was performed to determine the levels of circRNA_0094100 (circ_0094100) and microRNA-217 (miR-217). Western blot assay was carried out to measure the protein levels of proliferating cell nuclear antigen (PCNA), cyclin D1, B-cell lymphoma-2 (Bcl-2) and ATPase Na+/K+ transporting subunit beta 1 (ATP1B1). Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were conducted to verify the relationship between miR-217 and circ_0094100 or ATP1B1. Rapamycin treatment suppressed AML cell viability and promoted apoptosis in a dose-dependent way. Circ_0094100 was elevated in AML tissues and cells. Moreover, the circ_0094100 level was reduced in AML cells treated with rapamycin. Circ_0094100 knockdown further inhibited rapamycin-mediated AML cell viability and cell cycle and promoted cell apoptosis. Circ_0094100 silencing reduced the protein levels of PCNA, cyclin D1, and Bcl-2 in rapamycin-treated AML cells. For mechanism analysis, circ_0094100 acted as the sponge for miR-217 and miR-217 inhibition reversed circ_0094100 knockdown-mediated malignant behaviors of rapamycin-treated AML cells. Furthermore, miR-217 overexpression suppressed cell viability and cell cycle and facilitated apoptosis in rapamycin-exposed AML cells, which were abolished by increasing ATP1B1. Rapamycin inhibited AML cell viability and cell cycle process and induced apoptosis through regulation of the circ_0094100/miR-217/ATP1B1 axis.

A Route Clustering and Search Heuristic for Large-Scale Multidepot-Capacitated Arc Routing Problem.

The capacitated arc routing problem (CARP) has attracted much attention for its many practical applications. The large-scale multidepot CARP (LSMDCARP) is an important CARP variant, which is very challenging due to its vast search space. To solve LSMDCARP, we propose an iterative improvement heuristic, called route clustering and search heuristic (RoCaSH). In each iteration, it first (re)decomposes the original LSMDCARP into a set of smaller single-depot CARP subproblems using route cutting off and clustering techniques. Then, it solves each subproblem using the effective Ulusoy's split operator and local search. On one hand, the route clustering helps the search for each subproblem by focusing more on the promising areas. On the other hand, the subproblem solving provides better routes for the subsequent route cutting off and clustering, leading to better problem decomposition. The proposed RoCaSH was compared with the state-of-the-art MDCARP algorithms on a range of MDCARP instances, including different problem sizes. The experimental results showed that RoCaSH significantly outperformed the state-of-the-art algorithms, especially for the large-scale instances. It managed to achieve much better solutions within a much shorter computational time.

Strong Tribocatalytic Nitrogen Fixation of Graphite Carbon Nitride g-C3N4 through Harvesting Friction Energy.

Mechanical energy derived from friction is a kind of clean energy which is ubiquitous in nature. In this research, two-dimensional graphite carbon nitride (g-C3N4) is successfully applied to the conversion of nitrogen (N2) fixation through collecting the mechanical energy generated from the friction between a g-C3N4 catalyst and a stirring rod. At the stirring speed of 1000 r/min, the tribocatalytic ammonia radical (NH4+) generation rate of g-C3N4 can achieve 100.56 µmol·L-1·g-1·h-1 using methanol as a positive charge scavenger, which is 3.91 times higher than that without any scavengers. Meanwhile, ammonia is not generated without a catalyst or contact between the g-C3N4 catalyst and the stirring rod. The tribocatalytic effect originates from the friction between the g-C3N4 catalyst and the stirring rod which results in the charges transfer crossing the contact interface, then the positive and negative charges remain on the catalyst and the stirring rod respectively, which can further react with the substance dissolved in the reaction solution to achieve the conversion of N2 to ammonia. The effects of number and stirring speed of the rods on the performance of g-C3N4 tribocatalytic N2 fixation are further investigated. This excellent and efficient tribocatalysis can provide a potential avenue towards harvesting the mechanical energy in a natural environment.

Toward a reduced meat diet: University North American students' acceptance of a blended meat-mushroom burger.

Reduction of meat intake and increase in vegetable consumption have attracted considerable attention from researchers and food businesses. We conducted a field experiment in a university canteen with the aim of investigating the main behavioral factors determining the consumption of a blended meat-mushroom burger. 296 students who consumed the blended burger completed a structured survey including hedonic and attitudinal questions. We then contacted the same sample after 1 month to measure their reported behavior. Our results show that providing information highlighting the sustainability attributes of mushrooms has the most significant and positive impact on acceptability in comparison to information related to nutrition and indulgence. In addition, the participants' beliefs about the health and sustainable benefits of mushrooms positively impact their attitude toward the blended burger. This then significantly influences their behavioral intention to purchase the product, which proves to be a good predictor of the consumption behavior. Our findings suggest marketing opportunities arising from blending plant-based ingredients with meat products.

Decrease of the OFF state current of carbon nanotube field effect transistors via continuous repeated gate sweeping.

Continuous repeated gate sweeping incorporated with substrate etching step is utilized to decrease the OFF state current in single-walled carbon nanotube field effect transistors with bundled carbon nanotubes. In particular, the effects of continuous repeated gate sweeping on transfer characteristic of transistors are examined. The etching step creates suspension in transistors at contact with metal electrodes as well as causing some single-walled carbon nanotubes to dramatically burn off by electrical current. By repeating gate sweeping, source-drain current gets smaller and smaller. This will eventually lead to the OFF state current less than 2 nA. Defects in the lattice of single-walled carbon nanotubes introduced by multiple gate sweeping could be the reason for this phenomenon. Contribution from possible hole trapping is also considered.

Evolutionary Multiobjective Optimization Driven by Generative Adversarial Networks (GANs).

Recently, increasing works have been proposed to drive evolutionary algorithms using machine-learning models. Usually, the performance of such model-based evolutionary algorithms is highly dependent on the training qualities of the adopted models. Since it usually requires a certain amount of data (i.e., the candidate solutions generated by the algorithms) for model training, the performance deteriorates rapidly with the increase of the problem scales due to the curse of dimensionality. To address this issue, we propose a multiobjective evolutionary algorithm driven by the generative adversarial networks (GANs). At each generation of the proposed algorithm, the parent solutions are first classified into real and fake samples to train the GANs; then the offspring solutions are sampled by the trained GANs. Thanks to the powerful generative ability of the GANs, our proposed algorithm is capable of generating promising offspring solutions in high-dimensional decision space with limited training data. The proposed algorithm is tested on ten benchmark problems with up to 200 decision variables. The experimental results on these test problems demonstrate the effectiveness of the proposed algorithm.

Effects of Alkyl Side Chains of Small Molecule Donors on Morphology and the Photovoltaic Property of All-Small-Molecule Solar Cells.

Unraveling the relationship between nanoscale morphology of active layers and chemical structures of organic semiconductor photovoltaic materials is crucially important for further advancing the development of all-small-molecule organic solar cells (SM-OSCs). Here, in order to delve into the effect of flexible side chains of small molecule donors on the photovoltaic properties of SM-OSCs, we synthesized two new small molecule donors substituted by different flexible alkyl chains (iso-octyl chains for SM1-EH and n-octyl chains for SM1-Oct). As a result, the two small molecules present different absorption properties, energy levels, and stacking characteristics. When blending with Y6 as an acceptor, the SM1-Oct-based SM-OSC demonstrated a higher PCE value of 11.73%, while the SM1-EH-based device presents a relatively poorer PCE value of 8.42%. In addition, the morphology analysis demonstrated that, compared with the SM1-EH:Y6 blend, the SM1-Oct:Y6 blend film displayed better molecular stacking properties with stronger multilevel diffraction and preferable phase separation, resulting in the higher hole mobility, more efficient charge separation efficiency, and better device performance. These results underline that reasonably adjusting the flexible alkyl chains of small molecule donors can be an effective approach to further advance the development of the SM-OSCs field.

[Study on the excitation mechanism of upconversion red emission from Er3+ under square wave excitation].

The rise and decay curves of Er3+ 4F9/2 upconversion emission in oxyfluoride tellurite glass were measured under the excitation at 808 nm from a laser diode driven by square waves. The lifetime of the intermediate state could be determined via rise times. Then the accumulation process of the 4F9/2 population was confirmed. The excitation mechanism of up-conversion red emission under 808 nm excitation was confirmed by the rate equations and analyzing the relationship between the time constants of the rise and decay processes and the intermediate state. Square wave excited upconversion emission may also be used for measuring lifetimes of infrared energy levels with a conventional photomultiplier tube.

Polymer hole-transport material improving thermal stability of inorganic perovskite solar cells.

Cesium-based inorganic perovskite solar cells (PSCs) are paid more attention because of their potential thermal stability. However, prevalent salt-doped 2,2',7,7'-tetrakis(N,N-dipmethoxyphenylamine)9,9'-spirobifluorene (Spiro-OMeTAD) as hole-transport materials (HTMs) for a high-efficiency inorganic device has an unfortunate defective thermal stability. In this study, we apply poly (3-hexylthiophene-2,5-diyl) (P3HT) as the HTM and design all-inorganic PSCs with an indium tin oxide (ITO)/SnO2/LiF/CsPbI3-xBrx/P3HT/Au structure. As a result, the CsPbI3-xBrx PSCs achieve an excellent performance of 15.84%. The P3HT HTM-based device exhibits good photo-stability, maintaining ∼80% of their initial power conversion efficiency over 280 h under one Sun irradiation. In addition, they also show better thermal stability compared with the traditional HTM Spiro-OMeTAD.

Multilevel storage and photoinduced-reset memory by an inorganic perovskite quantum-dot/polystyrene floating-gate organic transistor.

Inorganic halide perovskite quantum dots (IHP QDs) have been widely studied in optoelectronic devices because of their size-dependent tunable bandgaps, long electron-hole diffusion lengths and excellent absorption properties. Herein, a novel floating-gate organic field-effect transistor memory (FGOFETM) is demonstrated, comprising a floating-gate of IHP QDs embedded in a polystyrene matrix. Notably, the FGOFETM exhibits photoinduced-reset characteristic that allows data removal by photo irradiation. This feature makes low energy-consuming memory and innovative devices possible. The nonvolatile devices also show a large memory window (≈90 V), ultrahigh memory on/off ratio (over 107) and therefore excellent multilevel information storage, in which 4 recognizable non-volatile states and long retention time (up to 10 years) are obtained. This work not only offers an effective guideline of high-performance FGOFETMs, but also shows great potential to realize multilevel data storage under electrical programming and photoinduced-reset processes.

Formula for the phase velocity of electromagnetic waves.

A new formula for the phase velocity of electromagnetic waves presented by Chen [Appl. Phys. Lett. 88, 121125 (2006)] is investigated and discussed here. The difference between the result obtained with the new formula and that obtained directly using the phase term is small for a fundament-mode Gaussian laser beam. However, this difference is qualitative in some high-order Gaussian-mode laser beams. Using the new formula for such beams, discontinuities arise in the distribution of the phase velocity. This distribution is not rotationally symmetric with respect to the optical axis, and an imaginary phase velocity may appear near these discontinuities.