Sharif Digital Repository

Targeting on the selenium free, pure sulfide kesterite compound (CZTS) allows retention of the higher band gap nontoxic absorber for a single-junction solar cell. In this work, CZTS thin films were deposited by the PLD method and the Structural/optical properties, as well as Mott–Schottky analysis, were studied at different substrate temperatures. Without undergoing the sulfurization process, the single-phase CZTS thin film is prepared at 300 ℃. In the second step, a numerical simulation is performed using the solar cell capacitance simulator to study the effect of the grading layer of MoS(Se)2 on the rear side of pure sulfide kesterite based solar cells. The device with a MoSe2 coated... 

The properties of colloidal nanoparticles are the key parameters in the fabrication of inexpensive solar cells based on the solution methods. In this study, Different nanostructures of CuInS2 (CIS) were successfully synthesized by a heating-up facile polyol-based method in which, polyols including diethylene glycol (DEG), ethylene glycol (EG), and glycerol (Gly) were chosen as both the solvent and the reductant. It is found that not only the indium precursor type but also the polyol solvent are greatly effective on the size, morphology and crystal phase of this sulfide ternary composition. Briefly, the heating-up synthesis using In(acac)3 in DEG and Gly media, created nano-sized particles... 

Low-cost inorganic hole-transporting materials (HTMs) accompanied by a printable carbon electrode is an efficient approach to address the limitation of material cost of perovskite solar cells (PSCs) and get this technology closer to commercialization. The present work is focused on optimizing the Zn/Sn ratio of Cu2ZnSnS4/carbon hole collectors in n-i-p structured PSCs, where CuInS2/carbon is applied as the reference hole collector. This composition regulation is a solution to address the challenge of composition-related defects of the Cu2ZnSnS4 (CZTS) material. The Zn/Sn ratio was tuned by the initial proportion of the zinc precursor during the nanoparticle (NP) synthesis using a heating-up... 

This work focused on the spray pyrolysis deposition of Cu2SnS3 (CTS) thin films using a stable basic solution. The effect of the most important parameters including the substrate temperature and copper concentration on the structural, optical and electrical properties of as-deposited thin films was investigated. Qualified thin films with suitable microstructure and composition could be deposited at 370℃. XRD and Raman analysis while confirming the pure CTS film formation, show that as the Cu/Sn decreases, the crystal structure layers are changed from the tetragonal phase to the cubic phase mixed with Sn-rich phases. The optical study shows its band gap between 1.08 and 1.2 eV for different... 

We investigate the use of simple nontoxic Cu2SnS3 (CTS) nanoparticles (NPs) as low-cost dopant-free hole-transport materials (HTMs) a substitute for spiro-OMeTAD in an n-i-p mesoscopic architecture of perovskite solar cells (PSCs). Besides, this work confirms the critical role of the crystalline phase of CTS NPs on the performance of the device. Using a facile one-pot heating-up procedure, pure zincblende and wurtzite structures of CTS NPs were obtained by sulfur element and thiourea as the sulfur source, respectively, and were dispersed in chloroform to make very stable nonpolar ink that is compatible with the perovskite. Nanoparticles with the wurtzite crystal phase showed much better... 

High-performance photodetectors play critical roles in numerous photon-based applications in imaging, communication, and energy harvesting. Nowadays, heterostructures have received significant attention to extend the performance of photodetectors, with exceptionally high optical absorption and a wide absorption range. However, the enhancement factors, exact mechanism, and facile fabrication procedures are long-standing problems. Here, a heterojunction of a two-dimensional chemical vapor deposition-grown monolayer of WSe2with a Cu2ZnSnS4(CZTS) film is introduced. The CZTS film as an abundant material was synthesized in the form of nanoparticles, and it showed a great effect on the enhancement... 

This study represents the investigation of In2S3 thin films, which have been deposited with different Indium salts (Chloride, Acetate, and Nitrate) using the Chemical Spray Pyrolysis (CSP) method. The Mott-Schottky analysis has been used in case of studying the electrical properties of films such as conduction and valence band, carrier densities, Fermi level (Efn), flat band potential, and semiconductor type. In the next step, the Rb1MAFA perovskite solar cell has been simulated, and the results have been validated by the experimental data (with the least parameters for fitting). Finally, In2S3 layers have been inserted on the SnO2 layer to decrease the recombination rate and enhance the... 

Utilizing carbon-laminated electrodes on perovskite solar cells (PSCs) benefits from simple fabrication process and low-cost material, in addition to enhanced stability. In this method, carbon foils are laminated on the underlying hole transport layer (HTL), so the HTL/carbon electrode interface is of the utmost importance in achieving high-performance devices. Here, we develop a conductive adhesive ink, consisting of poly methyl methacrylate (PMMA), highly conductive carbon black (HCCB), and CuInS2 (CIS) nanoparticles, as the interfacial adhesive layer between the underlying CIS HTL and the top carbon electrode. Utilizing carbon foil, wetted by the proposed optimized adhesive ink layer,... 

Using multiple antennas at the transmit and receive sides of a passive radar brings both the benefits of MIMO radar and passive radar. However one of the obstacles arisen in such configuration is the receive antennas placement in proper positions so that the radar performance is improved. Here we just consider the case of positioning one receiver among multiple illuminators of opportunity. Indeed it is a start for the solution of optimizing the geometry of the multiple receivers in a passive radar  

SbCl3 supported on montmorillonite K-10 is an efficient catalyst for the ring opening of epoxides with aromatic amines under solvent-free conditions and microwave irradiation to give the corresponding b-amino alcohols in high yields with high regioselectivity  

In this paper, we consider an integrated sensing and communication (ISAC) system with wireless power transfer (WPT) where an unmanned aerial vehicle (UAV)-based radar serves a group of energy-limited communication users in addition to its sensing functionality. In this architecture, the radar senses the environment in phase 1 (namely sensing phase) and mean-while, the communications users (nodes) harvest and store the energy from the radar transmit signal. The stored energy is then used for information transmission from the nodes to UAV in phase 2, i.e., uplink phase. Performance of the radar system depends on the transmit signal as well as the receive filter; the energy of the transmit... 

One of the important obstacles in MIMO (Multiple Input Multiple Output) radars is the issue of designing proper transmit signals. Indeed, the capability of signal design is a significant advantage in MIMO radars, through which, the system can achieve much better performance. Many different aspects of this performance improvement have been considered yet, and the transmit signals have been designed to attain such goal, e.g., getting higher SNR or better detector's performance at the receiver. However, an important tool for evaluating the radar's performance is its ambiguity function. In this paper, we consider the problem of transmit signal design, in order to optimize the ambiguity function... 

Two gains play key roles in recently developed MIMO wireless communication systems: "spatial diversity" gain and "spatial multiplexing" gain. The diversity gain refers to the capability to decrease the error rate of the MIMO channel, while the multiplexing gain implicitly refers to the amount of increase in the capacity of the MIMO channel. It has been shown that there is a fundamental tradeoff between these two types of gains, meaning interplay between increasing reliability (via an increase in the diversity gain) and increasing data rate (via an increase in the multiplexing gain). On the other hand, recently, MIMO radars have attracted much attention for their superior ability to enhance... 

It is a well known fact that using multiple antennas at transmit and receive sides improves the detection performance. However, in such multiple-input multiple-output (MIMO) configuration, proper positioning of transmitters and receivers is a big challenge that can have significant influence on the performance of the overall system. In addition, determining the power of each transmitter under a total power constraint is a problem that should be solved in order to enhance the performance and coverage of such a system. In this paper, we design the Neyman-Pearson detector under the Rayleigh scatter model and use it to introduce a criterion for the antenna placement at both transmit and receive... 

There has been much interest, recently, towards exploiting the Multiple-Input Multiple-Output (MIMO) technique in radar. It is shown that using multiple antennas at transmit and receive sides can improve the performance of the system. However, in order to analyze the system's performance, its ambiguity function, i.e. the ambiguity function of a MIMO radar, is needed to be defined. In this paper, beginning from the information theoretic definitions, we derive such function, specifically for a MIMO radar with widely separated antennas  

By combining the two ideas of MIMO (Multiple Input Multiple Output) and PCL (Passive Coherent Location) in radar, one can achieve the advantages of both recently developed techniques simultaneously. While using multiple antennas at the receive side provides a spatial diversity of the object to be detected, using multiple illuminators of opportunity, most importantly, makes the radar covert to the interceptors. One obstacle in such MIMO configuration is choosing the positions of the receive antennas. In this paper, after analyzing the Neyman-Pearson detector for the DVB-T based PCL, we introduce the probability of missed detection as a criterion to place the receive antenna. Here, we only... 

One of the most important obstacles in passive radar applications is removing the direct signal from the target channel. Otherwise, week echoes from the targets in the target channel would be ignored due to the limited dynamic range of the system. One of the most effective techniques in this field is using adaptive filters. In this paper various adaptive filters are introduced and their performances are shown and compared  

It has been shown that using multiple antennas in a radar system improves the performance considerably, since multiple target echoes are received from different aspect angles of the target. In this way, the target detection is improved. However, when using multiple antennas, some problems, such as designing the transmit signals, synchronization, etc. emerge that should be solved. One of such problems is the receiver placement. Receiver placement deals with choosing a proper position for the receive antenna in order to optimize the whole system's performance. In this paper, a receiver placement procedure based on improving the radar ambiguity function is proposed for the case of a multisite... 

By employing the MIMO (multiple-input-multiple-output) technology in radar, some new problems emerged, that, in order to benefit the MIMO gains in radar, it was necessary to solve them suitably. One of such obstacles is determining the positions of receive antennas in a MIMO radar system with widely separated antennas (WS MIMO radar), since it is shown that the antennas' positions affect the whole system's performance considerably. In this study, a proper receivers' positioning procedure is proposed. To do this end, four criteria are developed based on the proposed MIMO detector and the MIMO ambiguity function. The simulations verify that the proposed positioning procedure improves the... 

Phenols and alcohols are silylated with hexamethyldisilazane (HMDS) under microwave irradiation in solvent-free condition in good to excellent yields