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A review of the perovskite solar cells
Yao Xin, Ding Yan-Li, Zhang Xiao-Dan, Zhao Ying
2015, 64 (3): 038805. doi: 10.7498/aps.64.038805
Abstract +
The efficiency of solar cells based on organic-inorganic hybrid perovskite materials has a rapid growth from 3.8% in 2009 to 19.3%. The perovskite material (CH3NH3PbX3) exhibits advantages of high absorbing coefficient, low cost, and easily synthesised, which achieved extremely rapid development in recent years and gains great concern from the academic circle. As we know, perovskite materials not only serve as light absorption layer, but also can be used as either electron or hole transport layer. Consequently, various structures are designed based on the function of the perovskite, such as the solid-state mesoscopic heterojunction, meso-superstructured planar-heterojunction, HTM-free and the organic structured layers. Besides, it is also attractive for its versatility in fabrication techniques: one-step precursor solution deposition, two-step sequential deposition, dual-source vapor deposition, and vapor-assisted solution processing etc. This review mainly introduces the development and mechanism of the perovskite solar cells performance and the fabrication methods of peroskite films, briefly describes the specific function and improvement of each layer, and finally discusses the challenges we are facing and the development prospects, in order to have a further understanding of perovskite solar cells and lay a solid foundation for the preparation of new structures of the perovskite solar cells.
Magnetic structures, magnetic domains and topological magnetic textures of magnetic materials
Zhang Zhi-Dong
2015, 64 (6): 067503. doi: 10.7498/aps.64.067503
Abstract +
This article first gives a brief review of magnetic structures, magnetic domains and topological magnetic textures and their relations. On the one hand, the magnetic domains are determined by the magnetic structures, the intrinsic magnetic properties and the micro-structural factors of a material. On the other hand, the magnetic domains could control the magnetization and demagnetization processes and also the technical magnetic properties of a material. Topology is found to have a close relation with physical properties of material. Recent interest has focused on topological magnetic textures, such as vortex, bubble, meron, skyrmion, and it has been found that the topological behaviors of these topological textures are closely related with magnetic properties of a material. Then this article introduces recent advances in magnetic structures, magnetic domains and topological magnetic textures, from views of the size effect, defects and interfaces. Finally, this article reviews briefly some results of investigation on the relations between microstructures, magnetic domains and magnetic properties of rare-earth permanent magnetic thin films, the topological magnetic textures and their dynamic behaviors of exchange coupled nanodisks. It has been concluded from the reviews on the literature that the investigation on anisotropic exchange-coupled rare-earth permanent magnets with high performance benefits the high efficient utilization of rare-earth resources. One could achieve optimal magnetic properties through magnetic domain engineering by adjusting the microstructures of magnetic materials. The concepts of topology is applied to various research fields, while the contributions from topological behaviors to physical properties are discovered in different materials. The researches on magnetic domains, topological magnetic ground state and excitation states and their dynamic behaviors are very important for a better understanding of quantum topological phase transitions and other topological relevant phenomena. It can be quite helpful for understanding the correlation between different topological states and their relationship with magnetic properties of a material, and also it will definitely contribute to the applications in various fields of magnetic materials.
progress in electron-transport materials in application of perovskite solar cells
Ting Hung-Kit, Ni Lu, Ma Sheng-Bo, Ma Ying-Zhuang, Xiao Li-Xin, Chen Zhi-Jian
2015, 64 (3): 038802. doi: 10.7498/aps.64.038802
Abstract +
Ever since the first organic-inorganic hybrid halogen perovskite solar cell was first used as a photo-voltaic material in 2009, reports on this type of solar cell have grown exponentially over the years. Up till May 2014, the photo-energy conversion efficiency of the perovskite solar cell have already achieved an efficiency approaching 20%. Surpassing the efficiency achieved by organic and dye synthesized solar cell, the perovskite solar cell is in good hope of reaching the efficiency compatible with that of mono-crystalline silicon solar cell, thus it is going to be the star in photo-voltaic industry. In a perovskite solar cell, the film-formation and electron-mobility in the electron transfer layer can dramatically affect its efficiency and life-span. Especially in the up-right structured device, the mesoscopic structures of the electron-transfer layer will directly influence the growth of the perovskite layer. The present researches of electron transport materials mainly focus on three aspects: (1) How to improve the instability in mesoporous TiO2-mesosuperstructured solar cells, that arises from light-induced desorption of surface-adsorbed oxygen. (2) How to obtain TiO2 or other electron transport materials at low temperature (sub 150 ℃) in order to be applicatable in flexible devices. (3) How to substitute the mesoporous TiO2 or compact TiO2 transport layer by organic or composite materials. This article devides the materials that are used to make the electron-transfer layer into three distinct groups according to their chemical composition: i.e. metal oxides, organic small molecules, and composite materials, and introduces about the role they play and the recent development of them in constructing the perovskite solar cell.
Leveraging neighborhood “structural holes” to identifying key spreaders in social networks
Su Xiao-Ping, Song Yu-Rong
2015, 64 (2): 020101. doi: 10.7498/aps.64.020101
Abstract +
The identifying of influential nodes in large-scale complex networks is an important issue in optimizing network structure and enhancing robustness of a system. To measure the role of nodes, classic methods can help identify influential nodes, but they have some limitations to social networks. Local metric is simple but it can only take into account the neighbor size, and the topological connections among the neighbors are neglected, so it can not reflect the interaction between the nodes. The global metrics is difficult to use in large social networks because of the high computational complexity. Meanwhile, in the classic methods, the unique community characteristics of the social networks are not considered. To make a trade off between affections and efficiency, a local structural centrality measure is proposed which is based on nodes' a nd their ‘neighbors’ structural holes. Both the node degree and “bridge” property are reflected in computing node constraint index. SIR (Susceptible-Infected-Recovered) model is used to evaluate the ability to spread nodes. Simulations of four real networks show that our method can rank the capability of spreading nodes more accurately than other metrics. This algorithm has strong robustness when the network is subjected to sybil attacks.
Ranking key nodes in complex networks by considering structural holes
Han Zhong-Ming, Wu Yang, Tan Xu-Sheng, Duan Da-Gao, Yang Wei-Jie
2015, 64 (5): 058902. doi: 10.7498/aps.64.058902
Abstract +
Structural hole nodes in complex networks play important roles in the network information diffusion. Unfortunately, most of the existing methods of ranking key nodes do not integrate structural hole nodes and other key nodes. According to the relevant research on structural hole theory as well as the key node ranking methods, network constraint coefficient, betweenness centrality, hierarchy, efficiently, network size, PageRank and clustering coefficient, 7 metrics are selected to rank the key nodes. Based on the 7 metrics, a ranking learning method based on ListNet is introduced to solve ranking key nodes by multi metrics. Comprehensive experiments are conducted based on different artificial networks and real complex networks. Experimental results with manual annotation show that the ranking method can comprehensively consider the structural hole nodes and other nodes with different important features. The ranking results on different networks are highly consistent with the manual ranking results. The spreading experiment results using signed to interference ratio propagation model show that SIR model can reach a maximum propagating ratio in a shorter propagating time initiated by TOP-K key nodes selected by our method than TOP-K key nodes selected by other methods.
An information spreading model based on relative weight in social network
Wang Jin-Long, Liu Fang-Ai, Zhu Zhen-Fang
2015, 64 (5): 050501. doi: 10.7498/aps.64.050501
Abstract +
In this paper, we first introduce a mutual influence function among network nodes based on characteristics of information spreading in online social network. Then we put forward an information spreading model based on relative weight, analyze the propagation path and process of the network, and discuss the influence on different paths. Finally, the simulation experiments of the traditional SIR model and the model in this paper are conducted with six different network topologies. Results show that the two models have no significant difference in homogeneous networks, but there are significant differences in inhomogeneous networks. This result shows that the information spreading is influenced by the status of spreading nodes, and also shows that the real networks like Twitter and Sina Microblog have certain similarity in topological structure.
Internet public opinion chaotic prediction based on chaos theory and the improved radial basis function in neural networks
Wei De-Zhi, Chen Fu-Ji, Zheng Xiao-Xue
2015, 64 (11): 110503. doi: 10.7498/aps.64.110503
Abstract +
Information of internet public opinion is influenced by many netizens and net medias; characteristics of this information are non regular, stochastic, and may be expressed by a nonlinear complex evolution system. Corresponding model is difficult to establish and effectively predicted using the traditional methods based on statistical and machine learning. Characteristics of internet public opinion are chaotic, so the chaos theory can be introduced to research first, then the information of internet public opinion having chaotic characteristic is proved by the Lyapunov index. The model to predict the development trend of internet public opinion is next established by the phase space reconstruction theory. Finally, the hybrid algorithm EMPSO-RBF which is based on EM algorithm and the RBF neural network optimized by the improved PSO algorithm is proposed to solve the model. The hybrid algorithm fully takes the advantage of the EM clustering algorithm and the improved PSO, so the RBF neural network is improved by initializing the network structure in the early stage and optimizing the network parameters later. First, the EM clustering algorithm is used to obtain the center value and variance, and the radial basis function is improved with the combination of traditional Gauss model. Then the relevant network parameters are obtained by the improved PSO algorithm which is based on error optimizing the network parameters constantly. The model algorithm can be accurately simulated in the time series of chaotic information by experiments which are validated by different chaotic time series information; and it can better describe the development trend of different information of internet public opinion. The predicted results are made for government to monitor and guide the information of internet public opinion and benefit the social harmony and stability.
Design of an adaptive sliding mode controller for synchronization of fractional-order chaotic systems
Pan Guang, Wei Jing
2015, 64 (4): 040505. doi: 10.7498/aps.64.040505
Abstract +
In this paper, the synchronization of fractional-order chaotic systems is investigated. Based on sliding mode control and adaptive control theory, a fractional order integral sliding surface with strong robustness is designed, and an adaptive sliding controller is proposed for synchronizing the fractional-order chaotic systems with retaining the nonlinear part. Numerical simulations on synchronizing the Chen chaotic systems, the Liu chaotic systems, and Arneodo chaotic systems are carried out separately. The simulation results show the validity and feasibility of the adaptive sliding controller.
Recent advances in planar heterojunction organic-inorganic hybrid perovskite solar cells
Wang Fu-Zhi, Tan Zhan-Ao, Dai Song-Yuan, Li Yong-Fang
2015, 64 (3): 038401. doi: 10.7498/aps.64.038401
Abstract +
The development of highly efficient and low-cost solar cells is the key to large-scale application of solar photovoltaic technology. In recent years, the solution-processed organic-inorganic perovskite solar cells attracted considerable attention because of their advantages of high energy conversion efficiency, low cost, and ease of processing. The ambipolar semiconducting characteristic of perovskite enables the construction of planar heterojunction architecture to be possible in perovskite-based solar cells. This kind of architecture avoids the use of mesoporous metal oxide film, which simplifies the processing route and makes it easier to fabricate flexible and tandem perovskite-based solar cells. Planar heterojunction perovskite solar cells can be divided into n-i-p type and p-i-n type according to the charge flow direction. Two interfaces are formed between perovskite film and hole/electron transport layer, where efficient charge separation can be realized. Hole and electron transport layers can form separated continuous paths for the transport of holes and electrons, thus beneficial to improving exciton separation, charge transportation, and collection efficiency. In addition, this planar architecture avoids the use of high temperature sintered mesoporous metal oxide framework; this is beneficial to expanding the choice of the charge transport materials. In this paper, we review the recent progress on the planar heterojunction perovskite solar cells. First, we introduce the material properties of perovskite, the evolution of device architecture, and the working principle of p-i-n type and n-i-p type planar heterojunction perovskite solar cells. Then, we review the recent progress and optimization of planar heterojunction perovskite solar cells from every aspect of perovskite preparation and the selection of electron/hole transport materials. Finally, we would like to give a perspective view on and address the concerns about perovskite solar cells.
Synthesis and characterization of flower-like MoS2 microspheres by hydrothermal method
Fu Chong-Yuan, Xing Song, Shen Tao, Tai Bo, Dong Qian-Min, Shu Hai-Bo, Liang Pei
2015, 64 (1): 016102. doi: 10.7498/aps.64.016102
Abstract +
High-purity flower-like MoS2 microspheres have been successfully synthesized by hydrothermal method using Na2MoO4 and CH3CSNH2 as precursors, and H4O40SiW12 as an additive. Samples are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). XRD and EDS patterns show that the as-prepared samples are MoS2, which have good crystallinity with a well-stacked layered structure. SEM images show that the as-prepared MoS2 are composed of flower-like microspheres with a mean diameter about 300 nm, the structures of which are constructed from dozens of hundreds of MoS2 nano-sheet with a thickness of several nanometers. It is also found that the silicotungstic acid plays an important role in the formation of the flower-like MoS2 microspheres, which could affect the size and morphology of the MoS2. Flower-like MoS2 is not found in the as-prepared product without adding silicotungstic acid. A formation mechanism of MoS2 microspheres is tentatively given.
Adaptive fuzzy synchronization for uncertain fractional-order chaotic systems with unknown non-symmetrical control gain
Liu Heng, Li Sheng-Gang, Sun Ye-Guo, Wang Hong-Xing
2015, 64 (7): 070503. doi: 10.7498/aps.64.070503
Abstract +
In this paper the synchronization problem for the uncertain fractional-order chaotic systems with unknown non-symmetrical control gain matrices is investigated by means of adaptive fuzzy control. Fuzzy logic systems are employed to approximate the unknown nonlinear functions. We decompose the control gain matrix into a positive definite matrix, a unity upper triangular matrix, and a diagonal matrix with diagonal entries +1 or -1. The positive matrix is used to construct the Lyapunov function; the diagonal matrix is employed to design the controller. Based on the fractional Lyapunov stability theorem, an adaptive fuzzy controller, which is accompanied by fractional adaptation laws, is established. The proposed methods can guarantee the boundedness of the involved signals as well as the asymptotical convergence of the synchronization errors. It should be pointed out that the methods for using quadratic Lyapunov function in the stability analysis of the fractional-order chaotic systems are developed in this paper. Based on the results of this paper, many control methods which are valid for integer-order nonlinear systems can be extended to control fractional-order nonlinear systems. Finally, the effectiveness of the proposed methods is shown by simulation studies.
Photocatalytic application of Z-type system
Li Ping, Li Hai-Jin, Tu Wen-Guang, Zhou Yong, Zou Zhi-Gang
2015, 64 (9): 094209. doi: 10.7498/aps.64.094209
Abstract +
Z-type photocatlytic system, reflembling natural photosynthesis, consists of two different photocatalysts and a shuttle redox mediator, involving two-photon excitation process for photocatlysis. One photocatalyst as a photoreduction system offers the reduction sites by conduction band (CB) electrons, and the other photocatalyst as a photooxidation system provides the oxidation sites by valence band (VB) holes. A shuttle redox mediator as an electron conductor transfers the electrons from the CB of the photooxidation system to the VB of the photoreduction system. On the one hand, the separation of photocatalytic reactive sites is advantageous for spatial separation of the electrons and holes, which is beneficial for enhancing the photocatlytic activities. On the other hand, photoreduction system and photooxidation system of different materials effectively inhibit the reflerse reaction involvement of photoreductive and photooxidative products. The Z-type photocatlytic system simultaneously possesses a wide light absorption range and strong redox ability.
Vibration energy harvesting from a piezoelectric bistable system with two symmetric stops
Lan Chun-Bo, Qin Wei-Yang
2015, 64 (21): 210501. doi: 10.7498/aps.64.210501
Abstract +
Random vibration energy is widely existing in the environment. To efficiently harvest it, many researchers have designed lots of harvesters up till now. A lot of research works have found that when a harvester with bistable piezoelectric energy is excited by stochastic forces, if the intensity of them is low, the system's motion will be trapped in a single potential well. This will result in a low output voltage. In order to overcome the difficult of it and improve the harvesting efficiency, we develop an impact facility with two stops and incorporate it to a bi-stable energy harvester. This design can improve the harvesting efficiency greatly. First the electromechanical coupling equations are derived based on the Euler-Bernoulli beam theory and Kirchhoff's law. Then, we analyze the symmetric stops' effect on the potential function and the elastic restoring force of the system. Results show that both the potential energy and the magnitude of restoring force will be enhanced when collision takes place. Furthermore, we investigate the impact's effect on the system's dynamic responses and efficiency at harmonic excitation. Results reveal that a well designed impact can transform an intrawell motion into an interwell, and then increase the output voltage. And the chaotic motion can be changed into the large amplitude periodic one. Then, the harvester's dynamic responses under random excitations at a low intensity are obtained by using Euler-Maruyama method. Results indicate that the collision gaps can greatly influence the efficiency of the energy harvester. Collisions between the beam and the stops can force the system to oscillate between two potential wells more frequently. According to the relationship between the gap and the standard deviation of output voltage, we know that there exists an optimal collision gap for a definite intensity of stochastic excitation. The bistable energy harvester with this optimal gap will oscillate between the two wells frequently, and output a large voltage. Moreover, the collision stiffness can influence the system's performance as well. With the increase of collision stiffness, the system will exhibit a more frequently jumping between the two potential wells, but the stiffness has a limitation, exceeding which it cannot increase the frequency of jumping and improve the output power any more. So by properly designing the collision gap and stiffness, the system can most frequently jump between the two wells with a large amplitude of displacement, hence can attain the highest harvesting efficiency.
Real-time polarization difference underwater imaging based on Stokes vector
Guan Jin-Ge, Zhu Jing-Ping, Tian Heng, Hou Xun
2015, 64 (22): 224203. doi: 10.7498/aps.64.224203
Abstract +
Polarization difference imaging technique can effectively solve the underwater image deterioration problem that is caused by the interaction between light and water. Therefore, it has a significant application value in detecting and recognizing underwater target. In a traditional polarization difference imaging system, the object image is carried out by the common-mode rejection of background scattering light. However, the polarization state of the background scattering light is unknown, so the polarization difference imaging is realized by the irregular mechanical rotation of the optical polarization analyzer with two orthogonal polarization orientations. Therefore, it needs more time to determine the optimum detection angle of the polarization analyzer and cannot perform real-time underwater imaging, which restricts the rapid detecting function in the process of underwater imaging. In this paper, the detection principle of underwater polarization difference imaging is considered to exploit the difference in the polarization angle between background scattering light and target light. According to Marius's law, the physical model of polarization difference imaging is that the common-mode rejection of background scattering light will be achieved when the angles between the vibration direction of background and the two orthogonal polarization orientations are 45. Because the Stokes vector can be used to express the polarization angle of light, we propose the principle and construction of a computational polarization difference imaging system for real-time underwater imaging by incorporating the Stokes vector into the established model. It replaces the mechanical rotation of the polarization analyzer in a traditional polarization difference imaging system with the information processing of the Stokes vector. The experimental results show that the proposed method not only has the same effective performance as the conventional polarization difference imaging compared with the regular imaging, but also can improve the blurred imaging performance caused by an underwater scattering effect as well as increase the underwater detection distance. This method realizes rapid underwater target detection and recognition because it saves a large amount of time compared with the traditional one. Further, if we combine this method with the current polarization imaging instruments that capture the Stokes vector instantaneously, then a real-time automatic underwater polarization imaging can improve the efficiency of the underwater target detection and recognition. These findings are helpful for designing and developing the underwater polarization difference imaging systems.
The model of interdependent network based on positive/negativecorrelation of the degree and its robustness study
Chen Shi-Ming, Lü Hui, Xu Qing-Gang, Xu Yun-Fei, Lai Qiang
2015, 64 (4): 048902. doi: 10.7498/aps.64.048902
Abstract +
The model of interdependent network based on positive/negative correlation of the degree is constructed by the typical Barabási-Albert network in this paper. Dependency modality and dependency degree are considered in the model. Two parameters F and K are defined, which represent the proportion of dependency node and the redundancy of dependency, respectively. We study the influences of different values of F and K on the robustness of interdependent network in cascading failures under degree-based attacks and random attacks and also compare the results with those from the random interdependent network model. The simulation results show that the robustness of both random independency and interdependent network based on positive/negative correlation of the degree decreases as F increases and increases as K increases; in the model of full interdependence (F = 1), the robustness of interdependent network based on positive correlation of the degree is optimal under random attacks; the interdependent network based on negative correlation of the degree shows stronger robustness in the model of partial interdependence (F= 0.2, 0.5, 0.8). While the interdependent network based on positive correlation of the degree shows poorer robustness with any value of F under degree-based attacks.
Numerical simulation on stirring motion and mixing characteristics of ellipsoid particles
Liu Yang, Han Yan-Long, Jia Fu-Guo, Yao Li-Na, Wang Hui, Shi Yu-Fei
2015, 64 (11): 114501. doi: 10.7498/aps.64.114501
Abstract +
To investigate the motion characteristics and the law of identical property for particles obtained under segregation to uniform distribution conditions in forced agitation mixing, the mixing process of the same sized ellipsoidal particles at different rotating speeds in a U-tank is simulated using three-dimensional discrete element method. Macroscopic mixing law and partial mixing characteristics in particle mixing process are analysed in the view of single particle random motion trajectory and motion vector diagram of macroscopic particle flow. And the mathematical relation between mixability and revolutions of agitating blades is described quantitatively. Results show that convective mixing and four partial mixing characteristics control the mixing homogeneity process of identical property of segregation particles in forced agitation mixing. Mixability of segregation particles is independent of rotating speed of the agitating shaft, but has a direct correlation with revolutions. The relation between mixability and revolutions agrees with the exponential growth model. Research results can provide the basis and reference for equipment improvement and operating control of bulk material in the industry of the augmenting of mix.
Randomness analysis of lane formation in pedestrian counter flow based on improved lattice gas model
Li Ming-Hua, Yuan Zhen-Zhou, Xu Yan, Tian Jun-Fang
2015, 64 (1): 018903. doi: 10.7498/aps.64.018903
Abstract +
In this paper, we extend a lattice gas model recently proposed by Li et al, which considers the view field of pedestrian. An improved lattice gas model takes into account the effect of pedestrians' walking preference feature of empty area in the view field to simulate traffic dynamics of pedestrian counter flow. Three dynamic evolution processes under different pedestrian density are reproduced. The randomness of lane formation for different pedestrian density is found, and the probability of lane formation is given. Numerical simulations of relationship diagrams between the probability of lane formation and parameters of the system geometry size, the probability and the proportion of right walker flow, the probability and the strength of the drift, also the probability and the view field size are investigated. Results show that the extended model cannot form for the lane formation under a low pedestrian density, which is associated with the real pedestrian traffic. It is found that the density of pedestrian counter flow could be divided into 5 intervals, and there are differences in the dynamic evolution processes between these 5 intervals. This model and its result is useful for the study of the dynamic evolution process, and is helpful for raising efficiency of pedestrian counter flow in the channel.
Correlative analysis between the changes of surface solar radiation and its relationship with air pollution, as well as meteorological factor in eastern and western China in recent 50 years
Qi Yue, Fang Shi-Bo, Zhou Wen-Zuo
2015, 64 (8): 089201. doi: 10.7498/aps.64.089201
Abstract +
Based on the solar radiation information and climatic observation data from 1961 to 2011 in both East and West China, the interannual trends of surface solar radiation are investigated. By combining with cloud cover, sunshine percentage, sunshine duration, wind speed, atmospheric turbidity, and relative humidity, the causes affecting the variations of the total surface solar radiation in East China and West China are analyzed. The results show that the surface solar radiation decreased from 1961 to 2010 in both East and West China, but there was an abrupt change, which occurred in the early 1990s, followed by sustained increase. The surface solar radiation decreased from 1961 to 2010 in East China, and the decrease of surface solar radiation in the eastern region was greater than in the western region. The surface solar radiation is significantly correlated with sunshine duration in both East and West China. In East China, the surface solar radiation is significantly positively correlated with the percentage of sunshine. It indicates that the percentage of sunshine duration is the main factor affecting the total surface solar radiation in East China. The decrease of the total surface solar radiation is influenced by many factors. In East China, the percentage of sunshine and the atmospheric turbidity factor are the main factors affecting the surface solar radiation reduction. There is no correlation between cloud and ground solar total radiation. However, the percentage of sunshine is affected mainly by cloud cover and air pollution. In West China, no significant correlation is found between surface solar radiation and cloud cover, but significant correlation is detected between surface solar radiation and sunshine percentage. These indicate that the sunshine percentage could be a main factor affecting surface solar radiation. Wind becomes an important factor affecting the total surface solar radiation, since wind is a main factor expelling troposphere air pollution such as smog. A comparison of the variation in ground solar radiation between the East and West China shows that the aerosol particles of air pollution are the main factor affecting the reduction of total surface solar radiation in East China. Many scholars have found that the significant reduction of the surface solar radiation is mainly due to the absorption and scattering atmospheric aerosols. All these findings suggest that the air pollution has become an important factor affecting the surface solar total radiation, especially in East China.
For the first time fengyun3 C satellite-global navigation satellite system occultation sounder achieved spaceborne Bei Dou system radio occultation
Wang Shu-Zhi, Zhu Guang-Wu, Bai Wei-Hua, Liu Cong-Liang, Sun Yue-Qiang, Du Qi-Fei, Wang Xian-Yi, Meng Xiang-Guang, Yang Guang-Lin, Yang Zhong-Dong, Zhang Xiao-Xin, Bi Yan-Meng, Wang Dong-Wei, Xia Jun-Ming, Wu Di, Cai Yue-Rong, Han Ying
2015, 64 (8): 089301. doi: 10.7498/aps.64.089301
Abstract +
The radio occultation (RO) technique using signals from the global navigation satellite system, is widely used to observe the atmosphere for applications such as numerical weather prediction (NWP) and global climate monitoring. Since 1995, there have been turborogue sounder on board global positioning system/meteorology, black jack sounder on board challenging minisatellite payload and gravity recovery and climate experiment, IGOR sounder on board constellation observing system for meteorology, ionosphere and climate, GRAS on board meteorological operational, which have been recieving a large number of RO data, but their observed signals come only from global positioning system (GPS). These RO data have been wildly used in NWP and climate monitoring, however they cannot meet the requirements for high accuracy and real time atmosphere observation, in this case compatible RO sounder to obtain more RO observations is significant. Global navigation satellite system occultation sounder (GNOS) on board the fengyun3 C (FY3 C) satellite, which is the first Bei Dou system (BDS)/GPS compatible RO sounder in the world, was launched on 23 September 2013. Up to now, lots of RO observations have been obtained. In this study, the components of GNOS are introduced; one-day GNOS RO events and their global distribution are analyzed; compared with the GPS RO observations, the accuracy and consistency of BDS real-time positioning results and BDS RO products are analyzed. The preliminary results show that the BDS can enhance the number of RO events by 33.3%; the average deviation and standard deviation of BDS real time positioning results are 6 m and 7 m, respectively; the BDS/GPS difference standard deviation of refrectivity, temperature, humidity, pressure and ionospheric electron density are lower than 2%, 2 K, 1.5 g/kg, 2%, and 15.6%, respectively. The BDS observations/products are consistent with those of GPS, therefore BDS RO products can bring benefit to numerical wheather prediction and global chlimate change analysis.
Progress of research on new hole transporting materials used in perovskite solar cells
Song Zhi-Hao, Wang Shi-Rong, Xiao Yin, Li Xiang-Gao
2015, 64 (3): 033301. doi: 10.7498/aps.64.033301
Abstract +
Perovskite solar cells with a solid-state thin film structure have attracted great attention in recent years due to their simple structure, low production cost and superb photovoltaic performance. Because of the boost in power conversion efficiency (PCE) in short intervals from 3.8% to 19.3% at present, this hybrid cells have been considered as the next generation photovoltaic devices. It is expected that the efficiencies of individual devices could ultimately achieve 25%, which is comparable to the single-crystal silicon solar cell.In this article, the perovskite absorber, its basic device structure, and operating principles are briefly introduced. Since most of the high efficiency perovskite solar cells employ hole transporting materials (HTM), they could benefit the hole transport and improve the metal-semiconductor interface in the cells. This perspective gives analyses of some effective hole transporting materials for perovskite solar cell application. The hole transporting materials used in perovskite solar cell are classified into six categories according to their structures, including triphenylamine-based small molecule HTM, small molecule HTM containing N atom, sulfur-based small molecule HTM, sulfur-based polymer HTM, polymer HTM containing N atom and inorganic HTM. Emphasis is placed on the interplay of molecular structures, energy levels, and charge carrier mobility as well as device parameters. A critial look at various approaches applied to achieve desired materials and device performance is provided to assist in the identification of new directions and further advances.
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