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Discovering diverse significant regions (e.g., beaks and wings for some bird species) and extracting discriminative features from them is vitally important in fine-grained image recognition. Currently, the attention-based approaches present promising performance, which generally extract the fine-grained features by cropping or sampling significant parts. However, the cropping methods usually suffer from a fixed number of parts and difficulty to highlight irregular regions, and existing sampling methods may produce extremely distorted images. To effectively capture the fine-grained features, we propose an end-to-end separated smooth sampling network (SSSNet) in this paper. Specifically, we propose a separated smooth sampling module to highlight diverse significant regions of an image. Different from previous methods, we adopt smooth sampling on two separated coordinates to process images, which can effectively highlight discriminative contents and meanwhile avoid extreme distortion. We further propose an iterative masking method to embed into SSSNet, which can produce multiple attention maps without overlap to represent different significant regions. We conduct extensive experiments on CUB-200–2011, Stanford-Cars, and FGVC-Aircraft datasets. The results show the effectiveness of separated smooth sampling, and our SSSNet achieves better performance against previous state-of-the-art approaches under the same settings.

Irrespective of the success on reduction of contact resistivity, lack of chemical passivation of evaporated metal oxides heavily hinders their applications as passivating contacts, such contacts can be an alternative route for high efficiency and cost effective silicon solar cells. Here, we demonstrate that electron beam evaporated magnesium oxide (MgOx) thin film can work as a promising electron-selective passivating contact for n-Si solar cells after a post-annealing treatment and an alumina-initiated atomic hydrogenation. 10 nm MgOx on n-Si provided a surface recombination velocity down to 14.9 cm/s while 1 nm MgOx showed a low contact resistivity of 14 mΩ cm2. Comprehensive characterizations revealed the formation of Si–O–Mg bonds and the activation of atomic hydrogens were the main reasons for such high-level passivation. A PERC-like dopant-free rear contact was formed by using the 1 nm-MgOx as electron-collector and the 10 nm-MgOx as passivating layer, the resultant solar cells achieved 27% increment in efficiency and 51 mV increase in open-circuit voltage in comparison with reference devices. The ways of improving passivation quality of MgOx and novel design of contact structure open up the possibility of using evaporation-processed metal oxides as effective and low-cost carrier-selective passivating contacts for n-Si photovoltaic devices.

At present, it is a significant challenge to design electrode materials with both desirable electrochemical performance and high mass loading for supercapacitors by using a simple, efficient and safe method. With the introduction of Ni2+ ions, the hollow Ni-decorated Co9S8 nanospheres meeting the above requirements have been successfully synthesized by one-step electrodeposition method under a two-electrode system. As electrodes for supercapacitors, such Ni-decorated Co9S8 electrodes deliver an ultrahigh areal and volumetric specific capacitance of 5.64 F cm−2 and 171.85 F cm−3 at a current density of 1 mA cm−2, superior rate capability (88.9% retention at a current density of 20 mA cm−2) and remarkable cycling stability with a capacitance retention of 89% after 8500 cycles. Also, the as-fabricated flexible quasi-solid-state asymmetric supercapacitors based on Ni-decorated Co9S8 nanospheres and active carbon electrodes present high energy density. The practicability and operability of the device were successfully demonstrated by lighting up the LEDs with five different colors.

Black silicon (b-Si) with nanotextures is a promising light-trapping scheme for potentially achieving high conversion efficiency at reduced manufacturing cost in crystalline-silicon solar cells. However, the inherently high aspect-ratio and tiny feature size of the nanostructures are subject to severe surface (large surface areas) and Auger recombination (worse doping profile). These will abate the cost values of b-Si since one has to adopt a comprise strategy of applying shallow nanotextures with antireflection and passivation layers. Here, we show that silicon microwire solar cells featuring well-defined radial junctions can extensively suppress both surface and Auger recombination by providing excellent all-around electrical field. The radially doped silicon micropillar devices even show an internal quantum efficiency as good as that of planar substrate and their measured minority carrier lifetimes become nearly independent of total surface area. A great reduction in short-circuit current density loss was further identified as the junction abruptly changed from a fully diffused to a core-shell configuration, manifesting the powerful effectiveness of radial p-n+ junction on the suppression of Auger recombination. Furthermore, silicon microwire solar cell with a radial junction demonstrates 37% increase in efficiency compared with the reference cell, suggesting a feasible strategy towards high-efficiency solar devices.

Cobalt-based composites are generally investigated as cathode for supercapacitor due to its excellent electrochemical properties. Here, we explore its application as anode with the potential window of −0.3–0 V in 6 M KOH aqueous electrolyte. Interconnected Co3O4/CoO/Co(OH)2 nanosheets array is one-step electrodeposited on the surface of active carbon cloth, but showing low capacitance. Surprisingly, after in-situ compositing with MnO2 (ratio of Mn4+ is ∼23%), the hybrid MnO2/cobalt composites nanosheets array anode delivers ∼705 F g−1 at 0.68 A g−1, much higher than that of ∼161 F g−1 for pristine Co3O4/CoO/Co(OH)2. Besides, using NiCo2S4 nanosheet array@ nickel foam as cathode, the asymmetric supercapacitor exhibits high specific capacitance of 198 F g−1 at the current density of 0.5 A g−1. This work manifests a promising strategy to explore novel anode material and improve their properties, which holds great promise in energy storage/conversion devices.

For crystalline-silicon (c-Si) solar cells, the interdigitated back contact (IBC) structure has been long known as an efficient way to approach the theoretical limit of efficiency. However, the complexity of fabricating this kind of devices as well as the high dependence on expensive vacuum systems pose concerns about their commercial potential. Here, we demonstrate a novel c-Si IBC solar cell featuring dopant-free heterocontacts for both polarities, i.e. a solution-proceeded PEDOT:PSS film as hole-transporting layer (HTL) and an evaporated magnesium-oxide film as electron-transporting layer (ETL). Our innovatively buried ETL method provides substantial simplification on the architecture and fabrication of the IBC cells and makes it possible to adapt solution-proceeded HTLs while keeping good passivation in gap regions. The IBC solar cell shows an efficiency of 16.3%, with a promising short-circuit current density (Jsc) up to 38.4 mA/cm2. A thorough simulation concerning the influence of pitch size, surface recombination rate (at ETL and gap regions) was conducted, revealing a readily achievable Jsc of 41 mA/ cm 2 and a PCE beyond 22%. Our findings demonstrated a feasibility of using solution method to fabricate high efficiency dopant-free IBC solar cells.

This paper addresses the issue on how to more effectively coordinate the depth with RGB aiming at boosting the performance of RGB-D object detection. Particularly, we investigate two primary ideas under the CNN model: property derivation and property fusion. Firstly, we propose that the depth can be utilized not only as a type of extra information besides RGB but also to derive more visual properties for comprehensively describing the objects of interest. Then a two-stage learning framework consisting of property derivation and fusion is constructed. Here the properties can be derived either from the provided color/depth or their pairs (e.g. the geometry contour). Secondly, we explore the fusion methods of different properties in feature learning, which is boiled down to, under the CNN model, from which layer the properties should be fused together. The analysis shows that different semantic properties should be learned separately and combined before passing into the final classifier. Actually, such a detection way is in accordance with the mechanism of the primary visual cortex (V1) in brain. We experimentally evaluate the proposed method on the challenging datasets NYUD2 and SUN RGB-D, and both achieve remarkable performances that outperform the baselines.

Nanostructured silicon (Si) can provide improved light trapping capacity in Si/organic hybrid solar cells (HSCs) due to its low light reflectance compared with planar Si. However, the poor contact of nanostructured Si/organic interface and serious recombination on the uncovered Si surface can result in an inferior open-circuit voltage ( V OC ) and fill factor ( FF ) for HSCs. Here, we have designed and fabricated a novel cone-shaped Si nanoholes (SiNHs) structures to form a superior interface contact between SiNHs and organic layer by using an advanced metal assisted chemical etching method. In addition, a Cs 2 CO 3 layer was also introduced on the Si back surface to reduce the contact resistance as well as to suppress the surface recombination for the HSCs. With such improvements, a power conversion efficiency (PCE) up to 13.5% was achieved for Si/organic hybrid solar cell with the back passivation layer. This work provided a new strategy to improve the junction quality and performance of nanostructured Si/PEDOT:PSS HSCs.

The optical and electrical properties of PEDOT:PSS organic layer play a very important role in determining the power conversion efficiency (PCE) of Si–organic hybrid solar cells (HSCs). In the present study, properties of PEDOT:PSS thin films with reduced graphene oxide (rGO) and their impacts on the performances of the resultant Si–organic HSCs have been systematically investigated. The electrical conductivity of PEDOT:PSS improved 35% when rGO was added to PEDOT:PSS, and the fabricated HSCs with 2 mg/ml rGO addition yielded an PCE of 11.95% with a J sc of 31.94 mA cm −2 , a V oc of 579 mV and a FF of 0.648 . However, excess rGO would deteriorate the solar cells performances and it might create additional defects and prevent carriers being collected. The Raman spectroscopy, sheet resistance and EQE analyses with rGO suggested that the interaction between the conductive rGO flakes and the aromatic PEDOT most probably not only provide additional charge transport pathways in hole transport layer to improve carrier mobility leading to a higher carrier collection efficiency, but also suppress the electron recombination at the junction interface. In addition, the rGO serve as an antireflection coating to reduce the reflectance of PEDOT:PSS thin film leading to further enhanced performances of solar cells.

The increasing market growth of hybrid vehicles requires not only improvement on supercapacitor performance, but also cheap, abundant and sustainable material for supercapacitor fabrication. The present study demonstrated a novel strategy to convert used disposable bamboo chopsticks into uniform carbon fibers, and subsequently manganese dioxide (MnO 2 ) was conformably grown on each fiber to form a carbon fiber/MnO 2 composite. When it used as a self-supported binder-free electrode for supercapacitors, it delivered a superior mechanical stability, excellent rate capability, high specific capacitance of 375 F g −1 at the current density of 1 A g −1 and an increase specific capacitance was found after 5000 cycles interestingly. Moreover, the symmetric supercapacitor comprised of CFS/MnO 2 electrodes presents a maximum energy density of 11 Wh kg −1 and a maximum power density of 17.4 kW kg −1 . In addition, this approach presents a scalable, low-cost and sustainable route to transform chopsticks waste into carbon fibers to make electrodes for supercapacitors and lithium-ion capacitors.

3D flexible O/N co-doped graphene foams (GF) have been designed and fabricated successfully via combining the compression/hot curing strategy with chemical reduction and hydrothermal treatment, in which melamine foams were used not only as the source of N/O functional groups for the introduction of pseudocapacitance but also as the sacrificial template to inhibit the agglomeration of graphene. Also, the mechanism for method of the compressing/hot curing has been investigated systematically. And the resultant GF demonstrates excellent mechanical strength and flexibility. When the compacting GF is used as free-standing electrodes for supercapacitor, it exhibits more excellent ability of charge storage than that of pristine graphene foams. And 10 MPa-GF electrodes delivers high areal capacitance of 375 mu F cm(-2) at a current density of 1 A g(-1), excellent rate capabilities and superior cycling stability of above 100%. According to the analysis of capacitance contribution for 10 MPa-GF electrode, the pseudocapacitance originated from N/O functional groups is up to-65% of the contribution of total capacitance. Moreover, the symmetric supercapacitor comprised of 10 MPa-GF electrodes presents a maximum energy density of 16 Wh kg(-1) (8 Wh L-1) and a maximum power density of 17 kW kg(-1) (8.6 kW L-1). Published by Elsevier B.V.

Dopant-free heterojunction opens new doors to highly efficient silicon solar cells with interdigitated back-contacts (IBC) via an easy hard-mask processing. However, the existence of inevitable overlap between the hole- and electron-transport layers may cause edge leakage and recombination, which will deteriorate the power conversion efficiency. Here we unambiguously determined the edge recombination and recombination losses quantitatively, in combination with detailed comparisons in photovoltaic parameters, dark and light current-voltage (I–V) curves, partially illuminated I–V curves, of the hard-mask processed and the lithography processed IBC devices. Without the interfacial passivation layer, the solar cells fabricated by the hard-mask method suffer severe edge recombination with loss of 3 × 10−4 A and a quite poor fill factor (FF) of ~66%, suggesting that the edge recombination could be another important issue affecting the FF besides the series resistance. With the clear understanding of the edge effect, we finely control the edge overlap, and finally obtained silicon dopant-free solar cells (with of intrinsic amorphous silicon as passivation layer) with over 20% efficiency and 73% FF either by lithography or by hard-mask methods.

Single junction crystalline silicon (c-Si) solar cells featuring a conventionally doped interdigitated back contact heterojunction (IBC-SHJ) structure has approached a record efficiency of 26.6%, which is very close to the practical limit. However, integrating the interdigital p- and n-type amorphous silicon (a-Si:H) layers on the rear surface of Si substrate is of such complexity, posing problem of heavy dependences on expensive manufacturing techniques including plasma-enhanced chemical vapor deposition and photolithography. Its commercial potential is thus always being questioned, and to seek an alternative fabrication procedure, which adapts to cost-effective deposition parallel with simple patterning characteristics, has been a primary research target of related subjects. Here, we demonstrated 20.1% efficiency dopant-free IBC-SHJ solar cells by combining evaporated carrier-selective materials (MoOx and LiFx) and two-steps hard masks alignments, delivering substantial simplifications in the architecture and fabrication procedures. We investigated the effect of intrinsic a-Si:H films with different thicknesses on the passivation and contact resistance for both a-Si:H/MoOx and a-Si:H/LiFx contacts, showing 4 nm a-Si:H is better for high efficiency IBC-SHJ solar cells. We also found that the position of the metal target (electrode definition step) and isolation in between the busbar and the Si substrate are highly relevant to leakage and recombination and have great impact on the device performance. The dopant-free IBC-SHJ solar cells demonstrated here manifest enough confidence in our hard mask based fabrication procedure, with great potential for high performance-to-cost ratio in future.

In this work, we aim to solve the following multi-class inference problem: for given groups of unlabeled samples, a reliable multi-class classifier is expected to deterministically predict the label of each sample under the condition that only the class proportion information of each group is provided. Actually many modern applications can be abstracted to such a problem, e.g., large-scale images annotation, spam filtering, and improper content detection, where the class proportions of samples can be cheaply obtained while sample-wise labeling is prohibitive or quite hard. However, this problem has not been thoroughly investigated in previous works yet though it is much important in practice. The main challenging essentially lies on the severely under-determining itself. In this paper, we propose to utilize the natural sparsity of labels to alleviate this issue, and then formulate the classifier learning as a sparsity pursuit problem over a standard simplex. Moreover, due to the inapplicability of the popular @?"1-relaxation method for this case, we propose an optimization method to directly tackle the hard sparsity constraint, i.e., @?"0-constraint, based on the Augmented Lagrangian Multiplier (ALM) which can nicely provide a global convergence guarantee. It is noteworthy that our overall solution can not only directly predict the labels of the training and new samples, but also gracefully utilize the test samples to further boost the classification performance in a manner of semi-supervised learning. The experimental results on two benchmark datasets well validate the effectiveness of the proposed method.