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Bifacial semitransparent perovskite solar cells (BS-PSCs) have broad application prospects in the field of building-integrated photovoltaics, tandem solar cells as well as transparent chargeable devices. To fabricate high-performance BS-PSCs, the rear transparent electrode is one of the major obstacles should be overcome. Here, we develop a MoOx/Cu/Ag/MoOx multi-stacked electrode by thermal evaporation, and utilize it as a rear transparent electrode in the fabrication of high-performance n-i-p structure BS-PSCs. It is demonstrated that the minimum thickness required to obtain a continuous Ag film is reduced from 15 nm without the seed layer to 10 nm and the optical and electrical properties of multilayer transparent electrode are significantly enhanced. As a result, the BS-PSC device achieves the optimal power conversion efficiency of 13.44% at indium tin oxide side and 10.25% at MoOx/Cu/Ag/MoOx rear transparent electrode side, along with an average 8.67% optical transmittance for the visible light (400–800 nm) simultaneously. This work provides a promising approach to fabricate high-performance semitransparent and bifacial-operable optoelectronic devices in the future.

In recent years, public transport has been developing rapidly and producing large amounts of traffic data. Emerging big data-mining techniques enable the application of these data in a vari...

The introduction of nanostructures is an effective method to boost the photovoltaic performance of hybridized organic-inorganic halide perovskite-film solar cells. Taking into account their excellent light-scattering in the ultraviolet–visible range and their chemical inertness, silicon ( Si ) nanorods can be incorporated into the perovskite-film solar cells to enhance the light harvesting of the devices. By depositing Si nanorods between the prepared film and the substrate, the light scattering induced by the Si nanorods significantly promoted light absorption of the films. Moreover, resulting from the incorporation of Si nanorods, the enlarged grain size and compact structure of the films prolonged the lifetime of the carriers, which promoted the photoelectric properties of the perovskite films. By the appropriate incorporation of Si nanorods, the photovoltaic conversion efficiency of the CH 3 NH 3 Pb(Br 0.25 I 0.75 ) 3 -film-based solar cell was increased from 12.6% to 14.9% and the relative stability of the devices under dark humidity was improved. This strategy of employing low-cost and easily prepared Si nanorods to enhance the light harvesting of perovskite photovoltaic devices could be applied to photovoltaic devices based on perovskite films with other compositions.

Surface engineering of crystalline silicon (c-Si) is the core of Si-based semiconductor devices. The current commercially available c-Si solar cells achieve this by making use of a conventional thin dielectric film passivation system (TDFPS), including SiO2, Al2O3, SiNx:H and hydrogenated amorphous silicon (a-Si:H) in industry. However, the TDFPS requires high-vacuum and/or high-temperature conditions, which hinders efforts to further reduce the costs of device fabrication. A revolutionized approach to circumvent these issues involves the replacement of TDFPS with new material system which can also achieve high-quality passivation on c-Si surface. Here, we successfully establish and implement a functional group passivation system (FGPS) using a series of functional materials with a sulfonic functional group -SO3H, such as ‘poly(2-acrylamido-2-methylpropanesulfonic acid)’ (PAMPS) and ‘polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene, sulfonated, cross-linkable’ (PS-b-PERB), which can achieve a highly effective passivation on Si surface, resulting in power conversion efficiencies up to 20% when they are applied in the front surface engineering of interdigitated back contact (IBC) solar cells. Furthermore, the FGPS materials inherently allow passivation layer fabrication in lowtemperature and high-vacuum-free conditions. This work provides novel low-cost material strategies without compromise of performance for c-Si surface engineering in the future Si-based photovoltaics.

A growing number of megacities have been experiencing changes to their landscape due to rapid urbanization trajectories and travel behavior dynamics. Therefore, it is of great significance to investigate the distribution and evolution of a city's urban functional areas over different periods of time. Although the smart card automated fare collection system is already widely used, few studies have used smart card data to infer information about changes in urban functional areas, particularly in developing countries. Thus, this research aims to delineate the dynamic changes that have occurred in urban functional areas based on passengers' travel patterns, using Beijing as a case study. We established a Bayesian framework and applied a Gaussian mixture model derived from transit smart card data in order to gain insight into passengers' travel patterns at station level and then identify the dynamic changes in their corresponding urban functional areas. Our results show that Beijing can be clustered into five different functional areas based on the analysis of corresponding transit station functions: multimodal interchange hub and leisure area; residential area; employment area; mixed but mainly residential area; and mixed residential and employment area. In addition, we found that urban functional areas have experienced slight changes between 2014 and 2017. The findings can be used to inform urban planning strategies designed to tackle urban spatial structure issues, as well as guiding future policy evaluation of urban landscape pattern use.

In order to focus on the injury mechanism of electric cyclists in the collision accident between right turn of truck and electric bicycle, Pc-Crash is used to value the injury of the electric cyclist in this paper. Through repeated tests in Pc-Crash, it was found that two dynamic response process were existed. The electric bicycle and cyclist collided with truck, and the electric bicycle and cyclist were thrown to the ground due to the impact force. Finally, they were crushed under certain conditions. The multi-rigid-body truck model is built on the theories of multi-rigid-body modeling and multi-rigid-body collision to get the value of the crushed part which the single rigid model can't calculate. After that, we analyze HIC, continuous 3 ms resultant acceleration of chest, the shear force of femur and leg, based on the electric bicycle speed, the mass of electric bicycle and cyclist, the height of cyclist's seat. We found that when the electric cyclist is not crushed by the truck, the value of each damage index is below the threshold. But when the cyclist is crushed by the truck, the damage index of the part where the cyclist is crushed exceeds the threshold, and causes fatal injury to the cyclist. So, reducing the possibility of crushing can improve the safety level of electric cyclists.

Antimony selenide (Sb2Se3) has a one-dimensional (1D) crystal structure comprising of covalently bonded (Sb4Se6)n ribbons stacking together through van der Waals force. This special structure results in anisotropic optical and electrical properties. Currently, the photovoltaic device performance is dominated by the grain orientation in the Sb2Se3 thin film absorbers. Effective approaches to enhance the carrier collection and overall power-conversion efficiency are urgently required. Here, we report the construction of Sb2Se3 solar cells with high-quality Sb2Se3 nanorod arrays absorber along the [001] direction, which is beneficial for sun-light absorption and charge carrier extraction. An efficiency of 9.2%, which is the highest value reported so far for this type of solar cells, is achieved by junction interface engineering. Our cell design provides an approach to further improve the efficiency of Sb2Se3-based solar cells., Antimony selenide is a promising thin film solar cell absorber material in which grain orientation is crucial for high device performance. Here Li et al. grow the material in nanorod arrays along the [001] direction and obtain record high efficiency of 9.2%.

In this study, MgNd intermetallic is deposited as a thin film using magnetron sputtering. Ultraviolet photoelectron spectroscopy (UPS) is employed to determine the work function of the MgNd thin film. It is found that the MgNd thin film has a low work function of 3.5 eV, leading to its application in hybrid poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS)/n-Si solar cells as a back surface field (BSF) material. By introducing a MgNd thin film into the back Si/electrode interface of a hybrid solar cell, obvious improvements in the open circuit voltage (Voc) and fill factor (FF) of the device are observed, leading to an increase by more than 26% in power conversion efficiency (PCE). Temperature-dependent current density–voltage (J-V) and Voc-light intensity measurements demonstrate that the introduction of a MgNd thin layer increases the built-in voltage at the rear interface and decreases the recombination current in the device. These improvements are attributed to the efficacy of the MgNd thin film as a BSF by reducing minority carrier recombination and enhancing majority carrier transport.

In this paper, the CH3NH3PbBrXI3-X films were prepared by introducing CH3NH3Br into CH3NH3I precursor solution, after which the microstructure and photoelectric properties of the films were thoroughly investigated. Due to Br incorporation in the perovskite films, the band gap increased and the light absorption was slightly reduced while the charge carrier lifetime was prolonged due to the enhanced crystallinity. For the films with higher bromine content, the red shift of the photoluminescence peaks indicated that the phase segregation appeared in the films under illumination, which led to the formation of the iodine-rich domains in this process and the reduced carrier lifetime. On the contrary, for films with lower bromine content, the red shift of the photoluminescence peaks was negligible, which revealed that instability of the perovskite films under illumination can be suppressed by adjusting the bromine content of the films. Consequently, by moderate Br incorporation (CH3NH3Br/CH3NH3I mole ratio = 3:7), the CH3NH3PbBrXI3-X films with optimal photoelectric properties and photo-stability were achieved, and the stable photoelectric conversion efficiency of corresponding device under illumination can reach 13.8%.

The most important aspect in the development of Si-based photovoltaic technologies is the passivation of the Si wafer surface. Here, we show that Poly(3,4-ethylthiophene):polystyrenesulfonate (PEDOT:PSS) thin films, frequently used in organic/inorganic hybrid solar cells as emitter layers, provide an excellent surface passivation with a millisecond (ms) level effective minority carrier lifetime ( τ eff ). More importantly, we find that this passivation effect is dominated by the PSS species in PEDOT:PSS rather than PEDOT ones. The PSS thin film passivation yields a high τ eff of 9.4 ms on a high-resistivity Si wafer. The interface nature of PSS/Si is unveiled by the X-ray photoelectron spectroscopy and first-principles total-energy calculations together. An electrochemical passivation mechanism is clarified: the Si sub-oxides form at PSS/Si interface by the electrochemical grafting O groups in PSS onto Si surface, which can be controlled by injecting holes or electrons into the Si surface, leading to a switchable interface state between oxidation and deoxidation. To examine the application of the passivation strategy in real devices, we develop a polymer-passivated both-sides Si heterojunction solar cell with light-induced enhancement of photovoltaic performances, which is consistent with the light-induced enhancement of τ eff .

In this paper, we propose a novel Structure-Constrained Low-Rank and Partial Sparse Representation algorithm for image classification. First, a Structure-Constrained Low-Rank Dictionary Learning (SCLRDL) algorithm is proposed, which imposes both structure and low-rank restriction on the coefficient matrix. Second, under the assumption that the coefficient of test sample is sparse and correlated with the learned representation of training samples, we propose a Low-Rank and Partial Sparse Representation (LRPSR) algorithm which concatenates training samples and test sample to form a data matrix and finds a low-rank and sparse representation of the data matrix over learned dictionary by low-rank matrix recovery technique. Finally, we design a Sample Selection (SS) procedure to accelerate LRPSR. Experimental results on Caltech 101 and Caltech 256 show that our method outperforms most sparse or low-rank based image classification algorithm proposed recently. HighlightsWe propose a Structure-Constrained Low-Rank Dictionary Learning algorithm and develop its optimization strategy.We propose a Low-Rank and Partial Sparse Representation algorithm and develop its optimization strategy.We prove that the solution to LRPSR is block sparse for independent subdictionaries.We design a Sample Selection procudure to accelerate LRPSR.Experimental results show that our proposed method outperforms most sparse or low-rank based image classification algorithms proposed recently.

This paper picks out the key factors afiecting evacuation route choices and calibrates the corresponding choice model, which can serve the travel information publish and network system evaluation in the emergency evacuation. Time e‐ciency, information reliability and travel safety are criteria for the attributes selection. In the listed 9 candidate attributes, three (route length, delay time and delay-time reliability) of them are selected as the utility components by the method of Likert scale. A two-route stated preference survey is carried out to calibrate a C-logit model for the evacuation route choice which takes the aforementioned utility into account. Analysis results indicated that highly educated drivers are considered to be a group being risk averse. This information is useful to conduct a more correct model speciflcation of evacuation route choice and a more efiective control of tra‐c information in evacuation.

Disparity estimation for still images has attracted much interest and acquired many promising results. However, simply applying these methods to produce a disparity sequence may suffer from the undesirable flickering artifacts. These errors not only distinctly decrease the visible quality of the synthesized video, but also significantly reduce the coding efficiency of the disparity sequence. In this paper, a novel temporal consistency enhancement algorithm based on Guided Filter and Temporal Gradient (GFTG) is proposed. The flickering artifacts and noises are effectively removed and the edges of objects are well preserved. Both quantitative and qualitative evaluations show that the spatio-temporal consistency has been highly improved by utilizing our approach.

Recently, β-Ga2O3 solar-blind photodetectors (PDs) have been extensively investigated for a wide range of civil and military applications. Among them, the metal-semiconductor-metal (MSM) structure is one of the most popular candidates due to the merits of fabrication simplicity, the need for only one single-dopant active layer, easy integration with readout circuitry, high quantum efficiency, etc. However, there is generally a tradeoff between sensitivity and response speed due to the specific internal gain mechanism. In this work, MSM PDs based on the molecular beam epitaxy-grown β-Ga2O3 film were fabricated, and the metal/semiconductor (M/S) interfacial properties were tailored through the low-energy Ar-plasma pretreatment, resulting in the localized oxygen deficiency and a sharper interface. Accordingly, the PD sensitivity was dramatically improved, and the advantage of internal gain, i.e., high quantum efficiency, was preserved or became even larger. For example, the 60-W pretreated sample exhibited a high responsivity (R) of 8.41 A/W and a large specific detectivity (D*) of 1.24 × 1014 Jones, both increasing by one order of magnitude in comparison with the untreated sample. More interestingly, the response speed was unexpectedly accelerated, which is ascribed to the rapid and direct tunneling of electrons at the M/S interface as well as to the reduction in RC time constant based on the data analysis and the underlying physical principle discussion. The treatment conditions can be further optimized to counterbalance some side effects. These findings reveal an efficient technique for comprehensively improving the performance of β-Ga2O3 solar-blind PDs.Recently, β-Ga2O3 solar-blind photodetectors (PDs) have been extensively investigated for a wide range of civil and military applications. Among them, the metal-semiconductor-metal (MSM) structure is one of the most popular candidates due to the merits of fabrication simplicity, the need for only one single-dopant active layer, easy integration with readout circuitry, high quantum efficiency, etc. However, there is generally a tradeoff between sensitivity and response speed due to the specific internal gain mechanism. In this work, MSM PDs based on the molecular beam epitaxy-grown β-Ga2O3 film were fabricated, and the metal/semiconductor (M/S) interfacial properties were tailored through the low-energy Ar-plasma pretreatment, resulting in the localized oxygen deficiency and a sharper interface. Accordingly, the PD sensitivity was dramatically improved, and the advantage of internal gain, i.e., high quantum efficiency, was preserved or became even larger. For example, the 60-W pretreated sample exhibited a...

Various factors can make predicting bus passenger demand uncertain. In this study, a bilevel programming model for optimizing bus frequencies based on uncertain bus passenger demand is formulated. There are two terms constituting the upper-level objective. The first is transit network cost, consisting of the passengers’ expected travel time and operating costs, and the second is transit network robustness performance, indicated by the variance in passenger travel time. The second term reflects the risk aversion of decision maker, and it can make the most uncertain demand be met by the bus operation with the optimal transit frequency. With transit link’s proportional flow eigenvalues (mean and covariance) obtained from the lower-level model, the upper-level objective is formulated by the analytical method. In the lower-level model, the above two eigenvalues are calculated by analyzing the propagation of mean transit trips and their variation in the optimal strategy transit assignment process. The genetic algorithm (GA) used to solve the model is tested in an example network. Finally, the model is applied to determining optimal bus frequencies in the city of Liupanshui, China. The total cost of the transit system in Liupanshui can be reduced by about 6% via this method.

Light-induced degradation has been identified to be a critical issue for most silicon-based solar cell technologies. This study presents an observation of an opposite light-induced enhancement (LIE) effect in photovoltaic performance in poly(3,4-ethylthiophene):polystyrenesulfonate/n-Si organic-inorganic hybrid solar cells. The reduced density of interface states under light soaking (LS) is found to be responsible for the LIE of the hybrid solar cells. An increased minor carrier lifetime under LS and a switchable photoluminescence intensity while applying a voltage bias are observed, providing evidence for the underlying physical mechanism.

In this work, a magnesium (Mg) thin film with a low work function is introduced to obtain a downward energy band at the rear surface of a hybrid solar cell to achieve the function of a back surface field (BSF) similar to the conventional n-n+ high-low junction, i.e., favouring the majority carrier transport and suppressing minority carrier recombination. The open circuit voltages (Voc) of the hybrid solar cells with the Mg BSF layer achieve a clear improvement over those containing only the conventional metal electrode (e.g., Ag), resulting in an increase in the power conversion efficiency (PCE) of the hybrid solar cells from 9.2% to 12.3%. The Suns-Voc measurement determined using a Sinton tool gives Voc as a function of light intensity and shows that Voc increases linearly with the light intensity for the solar cell with the Mg BSF but increases first and then stabilises for the cells without the Mg BSF. This result is attributed to a difference in back surface recombination, further confirming the effi...

The use of polystyrenesulfonate (PSS) thin films in a high-quality passivation scheme involving the suppression of minority carrier recombination at the silicon surface is presented. PSS has been used as a dispersant for aqueous poly-3,4-ethylenedioxythiophene. In this work, PSS is coated as a form of thin film on a Si surface. A millisecond level minority carrier lifetime on a high resistivity Si wafer is obtained. The film thickness, oxygen content, and relative humidity are found to be important factors affecting the passivation quality. While applied to low resistivity silicon wafers, which are widely used for photovoltaic cell fabrication, this scheme yields relatively shorter lifetime, for example, 2.40 ms on n-type and 2.05 ms on p-type wafers with a resistivity of 1–5 Ω·cm. However, these lifetimes are still high enough to obtain high implied open circuit voltages (Voc) of 708 mV and 697 mV for n-type and p-type wafers, respectively. The formation of oxides at the PSS/Si interface is suggested to ...

In this paper, a novel Structure-Constrained Low-Rank and Partial Sparse Representation algorithm for image classification is proposed. First, a Structure-Constrained Low-Rank dictionary learning algorithm is proposed, which imposes both structure and low-rank restriction on the coefficient matrix. Second, under the assumption that the representation of test sample is sparse and correlated with the learned representation of training samples, we concatenate training samples and test samples to form a data matrix and find a low-rank and sparse representation of the data matrix over learned dictionary by low-rank matrix recovery technique. Experimental results demonstrate the effectiveness of the proposed algorithm.

In this paper, we present a novel local-based algorithm for stereo matching using Gabor-Feature-Image and Confidence-Mask. Various local-based schemes have been proposed in recent years, most of them mainly use color difference as evaluation criterion when constructing the initial cost volume, however, color channel is highly sensitive to noise, illumination changes, etc. Therefore, we develop a new cost function based on Gabor-Feature-Image for obtaining a more accurate matching cost volume. Furthermore, in order to eliminate the matching ambiguities brought by the winnertakes-all method, an effective disparity refinement strategy using Confidence-Mask is implemented to select and refine the less reliable pixels. The proposed algorithm ranks 23th out of over 150 (global-based and local-based) methods on Middlebury data sets, both quantitative and qualitative evaluation show that it is comparable to state-of-the-art local-based stereo matching algorithms.

Virtual view synthesis is widely used in multi-view video systems. However, artifacts and disocclusion areas along object boundaries caused by discontinuous values of depth map bring a new challenge to view synthesis. In this paper, a Global-background Based View Synthesis (GBVS) approach is proposed and it benefits the multi-view video to synthesize a virtual view when using Depth Image Based Rendering (DIBR). Firstly, inter-frame information is utilized to generate a global-background image. Then this global-background image is applied to complement the images which have been projected to the virtual view. Finally inpainting technology is employed to repair the still exposed regions. Both objective and subjective results illustrate that the proposed system provides a significant improvement in image quality. Additionally, compared with common view interpolation methods which depend on two or more reference views, the presented representation only requires one original view.

This paper presents a continuous traffic network design model that takes reliability and unreliability into account simultaneously under link capacity stochastic degradations. The upper level subprogram is a minimization of total mean-excess travel times subject to budgetary constraints and the lower level subprogram is a traffic assignment model called mean-excess user equilibrium model that explicitly considers both reliability and unreliability aspects under travel time variability. A solution algorithm based on genetic algorithm is developed to solve the proposed model. A numerical example is also conducted in order to illustrate the proposed model and the solution algorithm.

Urban transportation network is a complex, random and dynamic system. The resource saving of logistic distribution for companies is largely dependent on the reliable vehicle routing and planning of scheduling. Considering the complexity of urban transportation network, the non-recurrent traffic incidents often invalidate the predesigned optimal vehicle routing and scheduling planning and there also exists neglect of considering time-dependent variability of network under such a scenario. This paper is devoted to considering dynamic reliability analysis of network during lasting period of traffic incidents for formulating a specified vehicle routing model. Subsequently a heuristic genetic algorithm with Monte Carlo approach is applied to give a numerical result when the proposed model is testified under a certain case.

Link travel time prediction is a focus of intelligent transportation system (ITS) research. Through comparing the performances of the existing prediction algorithm, this article tries to integrate rough set and BP neural network to establish a new one for link travel time prediction. By comparing the predicted values of travel time to the real travel time, the predicted model is verified to be effective.

This paper studies the capacity reliability of a road network served by advanced traveler information systems (ATIS). Link capacities are treated as continuous random variables and a capacity reliability index introduced by Chootinan et al. (2003) is used to describe system performance. The logit-based stochastic user equilibrium (SUE) is used to characterize the travelers' route choice behaviors under influence of traveler information. A simulation based procedure is provided for the estimation of network reliability under ATIS. Numerical results of a test network show that the proposed approach can provide some new insights for assessing the impacts of ATIS on system performance.

In this paper, a block sparse discriminative classification framework (BSDC) is proposed under the assumption that a block or group structure exists in sparse coefficients on classification. First, we propose a block discriminative dictionary-learning (BDDL) algorithm, which learns class-specific subdictionaries and forces the sparse coefficients to be block sparse. An efficient gradient-based optimization strategy of BDDL also is developed, and the block sparse constraint of the sparse coefficient leads to a least-squares solution of nonzero entries in the sparse coding stage of dictionary learning. Second, to take advantage of the structures when a new test sample is given, conventional sparse coding algorithms are discarded, and structured sparse coding methods are adopted. Experiments validate the effectiveness of the proposed framework in face recognition and texture classification. We also show that BSDC is robust to noise.