Abstract ：

The aim of this paper is to analysis of distribution of shear stress of ribbon on the solar cell under temperature field. A new thermal stress analytical model of two-layer bonded structure based on physical mechanical law is established to calculate the distribution of shear stress. Through a series of calculation, the function of the distribution of shear stress can be obtained. Some meaningful conclusions which agree with practical production can be summarized as follows: shear stress is focused on the edges and, with the increase of temperature difference, the value of shear stress in the edge is more and more big.

Keyword ：

Analytical model silicon ribbon Thermal stress

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Abstract ：

During the course of solar module encapsulation, the output power of crystalline silicon solar module is less than the sum of the maximum output power of the constituents because of power loss. So it is very important to investigate the power loss caused by encapsulation materials and module production process. In this paper, the power loss of crystalline silicon solar module is investigated by experiments systematically for the first time. It is found that the power loss is mainly caused by the resistance of ribbon and mismatch of solar cells; the total power loss is as high as 3.93% for solar module composed of 72 cells (125 mm x 125 mm) connected in series. Analyzing and reducing the power losses are beneficial to optimizing encapsulation process for the solar module. The results presented in this study give out a direction to decreasing power loss and optimizing encapsulation process of crystalline silicon solar module.

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The so-called snail trails have caused enormous concerns. Many investigators are in a puzzle about the matter. In this paper we show that silver nanoparticles accumulating within the encapsulation foil cause the brownish discoloration. The source of silver is from silver phosphate impurities in EVA. The driving force accumulating the silver ions is offered by electric field when the solar cell operating outside and certain additives of encapsulation would react with silver ions to create darkened silver nanoparticles. Finally, we show here the effect of this phenomenon on the output power and reliability of photovoltaic power plant.

Keyword ：

additives crystalline silicon solar module encapsulation foil impurities nanoparticles snail trails

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The upgraded metallurgical silicon (UMG-Si) purified by a metallurgical process route directly is more energy efficient than the conventional Siemens process, but high metallic impurities are the cause of a large fraction of the total recombination events in solar cells made from UMG-Si. The efficiency of crystalline silicon solar cells made by such materials is lower than that from a chemical route, and UMG solar cells have big light-induced degradation. So, there always exist debates about using the upgraded metallurgical silicon for photovoltaic. In this paper, the impurity contents of silicon samples obtained in different stages were investigated, and a four-year verification of the largest UMG photovoltaic power plant in the world was conducted for the first time. The reliability, operating performance, and defects of UMG photovoltaic power plant were analyzed.

Keyword ：

Degradation Power plant Solar cells Upgraded metallurgical silicon

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Abstract ：

The long term reliability of crystalline solar modules is critical to the cost effectiveness and the commercial success of photovoltaic. The binding force reduction between silver paste and silicon leads to power degradation during subsequent qualification tests or outdoor using. Hence, it is very important to investigate the binding force of busbar and its influence. In this paper, the relationship between power degradation and the binding force of busbar was investigated. Significant results about binding strength of busbar were found as a result of different silver pastes. For crystalline silicon solar cells with 1.6 mm width busbar, the binding force between silver paste and silicon is not less than 2.0 N so as to let the modules made by such cells pass qualification tests. The results laid the foundation for studying the mechanical performance of front contact metallization system for screen-printed crystalline silicon solar cells. (C) 2013 Elsevier Ltd. All rights reserved.

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Abstract ：

According to the potential barriers generated by the silver, glass layer, and N+ emitter, an analytical model is developed to explain interface contact performance between the printed thick-film silver paste and emitter for crystalline silicon solar cells. According to the model, the front contact resistance between the sintered silver and N+ emitter is simulated at different doping concentrations, temperatures, and density of state. The quantitative expression of interface contact resistance between the printed thick-film silver paste and N+ emitter is derived for the first time. The results in this study unify different viewpoints about the current transport mechanisms at the sintered silver-silicon interface. If the glass frit chemistry and silver particle size are carefully tailored, the silver consumption per watt can be reduced, and the efficiency of crystalline silicon solar cells can be further improved. The results lay the foundation for studying the screen-printed crystalline silicon solar cell front contact metallization system. Copyright (c) 2013 John Wiley & Sons, Ltd.

Keyword ：

interface model silver pastes solar cells

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The aim of this work is to investigate the effect of soldering technology on solar module performance and reliability. In this study, the flux, the soldering temperature of soldering iron, and the annealing process during soldering process are investigated. Through a series of experiments, some meaningful conclusions which agree with practical production can be summarized as follows: it will be hard to joint if the flux with a low activity, while a too high activity will lead to corrosion at the same time; the optimal soldering temperature range is between 330 similar to 350 degrees C, which causes a low cell breakage rate and a high adhesion; annealing process can lead to less cell crack and low breakage rate by making copper more softer. These results have guiding significance for improving solar module manufacture and further enhancing module reliability and performance.

Keyword ：

adhesive strength manufacturing processes module reliability photovoltaic cells silicon

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The aim of this work is to investigate the effect of process on interfacial adhesion strength of Ag/Si for crystalline silicon solar cells. In this study, the width and thickness of busbar, the thickness of ribbon, and the soldering time and temperature during soldering process are investigated. Through a series of experiments, some meaningful conclusions which agreed with practical production can be summarized as follows: the thicker and wider the busbar is, the larger the adhesion force is; the thicker and stiffer the ribbon is, the smaller the adhesion force is; short soldering time and low soldering temperature are beneficial to enhancing the adhesion strength. These results have important guiding significance for improving solar cell manufacturing process and further enhancing the reliability of crystalline silicon solar cell.

Keyword ：

adhesive strength manufacturing processes photovoltaic cells silicon

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The rising conventional energy prices have opened up the market for photovoltaic, but the lack of polycrystalline silicon from the chemical route restricts the growth of crystalline silicon solar cells. Recently there is a trend that produces solar cells by using the newly developed solar grade silicon feedstock from a metallurgical process route. In this article, the chemical components of solar grade silicon feedstock are analyzed. The single crystalline silicon solar cells from 100% solar grade silicon feedstock from a metallurgical process route are investigated. The outdoor performance of solar modules encapsulated by such cells is reported. The experimental evidence suggests that such solar cells can achieve the average efficiency higher than 14% on single crystalline silicon wafers. However, the efficiency degradation of solar cells under natural sunlight is significant, and the electrical uniformity of small cells diced from the whole cell is too bad. The metal impurities, oxygen, carbon, and their complexes influence the performance stabilization. The article proves that the module made by such cells has a big cell mismatch loss than normal cells made by electronic grade silicon, even if these cells come from the same sort. And the operating temperature of the cells of the modules is 15-22 degrees C higher than normal modules under the same conditions. The solar grade silicon feedstock from a metallurgical process route has to be improved farther in order to be used in photovoltaic industry.

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Abstract The nonlinear optical polyimide (NLOPI) attached with azobenzene chromophore side-chain is synthesized by diazo coupling reaction of 4-nitrobenzenediazonium tetrafloroborate to poly(amic acid) in 1-methyl-2-pyrrolidone and imidization reaction at 250°C for 2 h. The photoisomerization property of the NLOPI is investigated. The effects of the laser reaction time and laser power on the photoisomerization property of NLOPI film are studied. When the NLOPI film is irradiated by the 532 nm YAG laser, the absorption peak of NLOPI at 500 nm decreases with rising the laser power and extending laser reaction time, while the absorption at 360 nm increases steadily. The third-order nonlinear optical property of the nonlinear optical polyimide attached with azobenzene chromophore side-chain was studied by Z-scan technology. On the effect of 532 nm laser, the nonlinear refractive index and nonlinear absorption properties of the NLOPI are all negative, which shows that the NLOPI is self-scattering media. The nonlinear refractive index (n2), nonlinear refractive coefficient (γ), nonlinear absorption coefficient (β) and the third-order nonlinear susceptibility (χ(3)) of the NLOPI are -1.62 × 10-7esu, -4.04 × 10-14m2/W, 3.98 × 10-8m/W and 3.41 × 10-18m2/W, respectively.

Keyword ：

Azobenzene chromophore Nonlinear absorption coefficient Nonlinear absorption properties Non-linear optical properties Nonlinear refractive index Third order nonlinear optical properties Third-order nonlinear susceptibility Z-scan

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