Preparation of SiC Porous Ceramics by Crystalline Silicon Cutting Waste

SiC porous ceramics were prepared at 1 400 ℃ for4 h with crystalline silicon cutting waste and activated carbon as main starting materials and NH4HCO3 as the pore-forming agent. Effects of NH4HCO3 additions( 0,20%,30%,40%,by mass) on the phase composition,microstructure,sintering properties,cold compressive strength and thermal shock resistance of as-prepared Si C porous ceramics were investigated. The results show that:( 1) addition of NH4HCO3 remarkably influences the apparent porosity and cold compressive strength of specimens. The apparent porosity achieves its maximum value( 63. 40%) when 40% NH4HCO3 is added,while the minimum cold compressive strength is 4. 77 MPa;( 2) the specimen with 40% NH4HCO3 has the best thermal shock resistance. The thermal cycling times between1 000 ℃ to room temperature reach 62;( 3) the addition of NH4HCO3 does not remarkably affect the phase composition of the specimens;( 4) the specimens include a large number of SiC particles and a small amount of SiC whiskers.

Enhanced Photovoltaic Properties for Rear Passivated Crystalline Silicon Solar Cells by Fabricating Boron Doped Local Back Surface Field

In order to enhance the p-type doping concentration in the LBSF, boron was added into the aluminum paste and boron doped local back surface field（B-LBSF） was successfully fabricated in this work. Through boron doping in the LBSF, much higher doping concentration was observed for the B-LBSF over the Al-LBSF. Higher doping concentration in the LBSF is expected to lead to better rear passivation and lower rear contact resistance. Based on one thousand pieces of solar cells for each type, it was found that the rear passivated crystalline silicon solar cells with B-LBSF showed statistical improvement in their photovoltaic properties over those with Al-LBSF.

Effects of Pore-forming Agents on Properties of Silicon Carbide Porous Ceramics Prepared from Crystalline Silicon Cutting Waste

SiC powder was rapidly synthesized in an induction furnace with crystalline silicon cutting waste and active carbon as raw materials,and then SiC porous ceramics were prepared at 1600 t for 4 h with carbon embedded using the powder as raw material,the starch and the graphite as pore-forming agents.Effects of additions of different pore-forming agents on the phase composition,microstructures,physical properties,and cold crushing strength of the porous ceramics were investigated.The results show that the main crystalline phases of the synthetic powder areα-S iC(6H-SiC)andβ-SiC(3C-SiC).The phase composition of the porous ceramics includesα-S iC(6H-SiC),β-SiC(3C-SiC),FeSi,quartz and Si2N20.The apparent porosity and closed porosity of the porous ceramics prepared by adding starch are higher,and the cold compressive strength of the porous ceramics added with graphite is higher.As increasing the additions of the starch,the apparent porosity,closed porosity and linear shrinkage ratio of the porous ceramics increase,and the bulk density decreases correspondingly.When 20 mass%starch is added,the apparent porosity,closed porosity,linear shrinkage ratio and cold compressive strength are 57.05%,2.03%,5.10%and 10.20 MPa,respectively.

Columnar growth of crystalline silicon films on aluminium-coated glass by inductively coupled plasma CVD at room temperature

Silicon films were grown on aluminium-coated glass by inductively coupled plasma CVD at room temperature using a mixture of SiH4 and H2 as the source gas. The microstructure of the films was evaluated using Raman spectroscopy, scanning electron microscopy and atomic force microscopy. It was found that the films are composed of columnar grains and their surfaces show a random and uniform distribution of silicon nanocones. Such a microstructure is highly advantageous to the application of the films in solar cells and electron emission devices. Field electron emission measurement of the films demonstrated that the threshold field strength is as low as -9.8V/μm and the electron emission characteristic is reproducible. In addition, a mechanism is suggested for the columnar growth of crystalline silicon films on aluminium-coated glass at room temperature.

Polarization effects and tests for crystalline silicon solar cells

We try to find a fast and simple potential induced degradation effect （PID） test procedure for crystalline silicon solar cells. With sodium chloride （NaC1） solution as Na＋ source, PVB as lamination material, we can carry out the test in 1 h. Solar cells with newly developed PID resistance process were also tested. The increase of reverse current of solar cell can be considered a key standard to determine if the solar cell was prone to PID. Moreover, it showed that the increase of reverse current for the PID resistance solar cell was less than 2. In addition, the test results of the solar cells fitted very well with that of the modules by standard procedure.

Numerical Analysis of Ingot Casting Processes for Quasi-Single Crystalline Silicon Solar Cells in the iDSS Furnace

Multi-crystalline silicon ingots produced using directional solidification systems(DSS)represent the best way to obtain high quality crystalline silicon at low prices and with high throughputs.The DSS technology is widespread among PV silicon ingot producers and hundreds of furnaces are manufactured worldwide every year.The present challenge for crystal growers is to increase the quality of ingot and to reduce the specific energy consumption and cost. The first goal can be reached by changing the DS process to a Mono-Like-Casting process,while the second one has pushed some companies to develop new DSS furnaces able to grow ingots up to 800 kg.The main features and the characteristic design of the hot-zone in the iDSS(induction-DSS)furnace are presented,also in comparison with the standard DSSs ones.The reduction of the thickness of insulation boards,the smaller size of the hot-zone and the selective lateral induction coil system lead to an optimal control of the thermal instabilities into the silicon melt,increasing the ingot quality.In fact,the lateral induction coil system is equipped with independent turns connections and it can be used to force selectively-at different vertical positions-the most suitable thermal condition.In this way,one is able to compensate the radiative thermal losses and create a 'virtual' adiabatic wall,producing a planar solidification front or modeling the radial thermal gradient in order to obtain the desired solidification front shapes.In previous papers,the authors have presented some preliminary results obtained with a iDSS furnace^([4][5][6]).In the present paper is proposed a discussion about the numerical analysis of Mono-Like-Casting process with iDSS furnace capacity up to 120 kg of silicon feedstock.The furnace is actually under construction in the context of research activities of PFV(Polo Fotovoltaico Veneto).

Determination of Particle Sizes and Crystalline Phases on Colloidal Silicon Nanoparticle Suspensions

Particle size and crystallinity of silicon nanoparticles were determined by analyzing the optical extinction spectra of colloidal suspensions. Experimental results from these colloids were anaiyzed using Mie theory in connection with effective medium theory, in order to determine particle sizes and their internal structure with the simple technique of optical transmission spectroscopy. By modeling an effective refractive index for the particles, the crystalline volume fraction can be extracted from extinction spectra in addition to information about the size. The crystalline volume fraction determined in this way were used to calibrate the ratio of the Raman cross sections for nanocrystalline and amorphous silicon, which was found to be σc./σa = 0.66

Amorphous/Crystalline （n-n） Si Heterojunction Photodetector Made by Q-Switched 0.532-mm Laser Pulses with Novel Technique

Amorphous/crystalline n-n-isotype Si heterojunetions are made by a pulsed Q-switched second harmonic generation Nd：YAG laser. The process includes melting and subsequently fast resolidification of a thin front layer of monocrystalline Si by laser pulses to create an amorphous layer （phase transition）. Different laser energy densities are used to form the amorphous layer on a monocrystalline Si substrate, the results of the electrical characteristics of the heterojunctions are dependent strongly on the laser energy density. Optoelectronic properties such as current-voltage, capacitance voltage, and spectral sensitivity are measured in a-Si/c-Si hereto junctions （in the absence of anti-reflecting coating and frontal grid contact） prepared by different laser energy densities. The built-in-potential values extracted from current-voltage measurements are close to the published results of （n-p） amorphous/crystalline hereto junction made by glow discharge and plasma enhanced chemical vapour deposition. Furthermore, examination of the formation of amorphous pattern on Si surface is carried out with the help of optical microscopy. Best photovoltaic performance is recognized to be at ,5.6 J/cm^2. The photodetector shows a wide spectral response, and the peak response is at 780nm. On the other hand, this peak is independent of laser energy.

Simulations of Heterojunction and Tandem Solar Cells Based on 3C Silicon Carbide

In order to improve the efficiency of solar cells based on cubic silicon carbide (3C-SiC), one heterojunction solar cell and two tandem structures were simulated under AM1.5 illumination using SCAPS software. The cells’ performances were studied according to the thickness of the silicon carbide layers. Simulation results allowed to achieve an efficiency of 22.03% with a tandem junction structure using an optimal thickness of 3C-SiC layer.

Development of metal-recycling technology in waste crystalline-silicon solar cells

Solar energy is currently one of the most promising clean energy sources and the use of solar energy has led to a rapid increase in the number of solar cells.As one of the fastest-growing electronic wastes,the resource treatment of solar cells at the end of their life should not be neglected.This review discusses the trend for the market development of crystalline-silicon solar cells and analyzes their physical structure and composition.It also discusses the current domestic and international recycling technologies for crystalline-silicon solar cells,including manual dismantling,inorganic acid dissolution,the combination of heat-treatment and chemical methods,and organic solvent dissolution.The shortcomings of the above treatment methods are discussed and some views on the recycling of waste crystalline-silicon solar cells are presented.Constructive suggestions for the green and sustainable development of crystalline-silicon solar cells are put forward by comparing different treatment-recycling processes.

Photovoltaic Cells and Modules towards Terawatt Era

Progresses in photovoltaic technologies over the past years are evident from the lower costs, the rising efficiency, to the great improvements in system reliability and yield. Cumulative installed power yearly growths were on an average more than 40% in the period from 2007 to 2016 and in 2016, the global cumulative photovoltaic power installed has reached 320 GWp. The level 0.5 TWp could be reached before 2020. The production processes in the solar industry still have great potential for optimization both wafer based and thin film technologies. Trends following from the present technology levels are discussed, also taking into account other parts of photovoltaic systems that influence the cost of electrical energy produced. Present developments in the three generations of photovoltaic modules are discussed along with the criteria for the selection of appropriate photovoltaic module manufacturing technologies. The wafer based crystalline silicon(csilicon) technologies have the role of workhorse of present photovoltaic power generation, representing more than 90% of total module production. Further technology improvements have to be implemented without significantly increasing costs per unit, despite the necessarily more complex manufacturing processes involved. The tandem of c-silicon and thin film cells is very promising. Durability may be a limiting factor of this technology due to the dependence of the produced electricity cost on the module service time.

Study of Quantitative and Qualitative Characteristics of Nickel Clusters and Semiconductor Structures

The possibility of building of clusters of impurity atoms of Ni in silicon and controlling their parameters is currently investigated in the present research article. Our group develops a special technique for doping, the so-called “low-temperature doping” of semiconductors. This method of doping is based upon the diffusion process which is carried out in stages by gradually increasing temperature ranging from room temperature to the diffusion temperature.

Study on the influence of standoff distance on substrate damage under an abrasive water jet process by molecular dynamics simulation

The process of a cluster-containing water jet impinging on a monocrystalline silicon substrate was studied by molecular dynamics simulation. The results show that as the standoff distance increases, the jet will gradually diverge. As a result, the solidified water film between the cluster and the substrate becomes "thicker" and "looser". The "thicker" and "looser" water film will then consume more input energy to achieve complete solidification, resulting in the stress region and the high-pressure region of the silicon substrate under small standoff distances to be significantly larger than those under large standoff distances. Therefore, the degree of damage sustained by the substrate will first experience a small change and then decrease quickly as the standoff distance increases. In summary, the occurrence and maintenance of complete solidification of the confined water film between the cluster and the substrate plays a decisive role in the level of damage formation on the silicon substrate. These findings are helpful for exploring the mechanism of an abrasive water jet.