In solar energy utilization, monocrystalline silicon and polysilicon also play a huge role. Although from now on, to make solar power have a larger market and be accepted by the majority of consumers, it is necessary to increase the photoelectric conversion efficiency of solar cells and reduce production costs. From the current international solar cell development process, we can see that its development trend is monocrystalline silicon, polycrystalline silicon, ribbon silicon, thin film materials (including microcrystalline silicon-based thin films, compound-based thin films, and dye thin films).
From the point of view of industrialization, the center of gravity has been developed from single crystal to polycrystalline. The main reasons are as follows: [1] The number of head and tail materials that can supply solar cells is getting less and less; [2] For solar cells, the square substrate is more Conveniently, the polysilicon obtained by the casting method and direct solidification method can directly obtain a square material; [3] The production process of polysilicon continues to progress, and a full-automatic casting furnace can produce silicon ingots of over 200 kg per production cycle (50 hours). The grain size reaches centimeters; [4] The research and development of monocrystalline silicon process in recent ten years is very fast, and the process is also applied to the production of polycrystalline silicon cells, such as selective etching of the emitter junction, back surface field, and corrosion of suede. , surface and body passivation, fine metal gate electrode, using screen printing technology can reduce the width of the gate electrode to 50 microns, height of 15 microns or more, rapid thermal annealing technology for polysilicon production can greatly shorten the process time, single The thermal process time can be completed within one minute, and the battery conversion efficiency of more than 14% is achieved on a 100 square centimeter polycrystalline silicon wafer using this process. According to reports, the current efficiency of a battery fabricated on a 50 to 60 micron polysilicon substrate exceeds 16%. The use of mechanical notching, screen printing technology on the 100 square cm polycrystalline efficiency of more than 17%, no mechanical groove in the same area efficiency of 16%, the use of buried grid structure, mechanical groove in the 130 square cm polycrystalline Battery efficiency reached 15.8%.
Chlorine dioxide when used as an effective disinfectant forms undesirable disinfection by-products, i.e. chlorite and chlorate ions. The aim of this research was to study the removal of these ions byferrous ions in the presence or absence of oxygen. The efficiency of Fe+2 for ClO2- and ClO3- removal was followed by a determination of their initial and final concentrations, pH and delta Fe+2 consumed/delta ClO2- removed ratios. The optimal weight ratio of delta Fe+2 consumed/delta ClO2- removed for complete ClO2 removal was found to be close to the theoretical calculated value of 3.31. It was proved that ferrous salts can reduce chlorite ions to harmless Cl- ions. This method can be recommended as a part of ClO2 disinfection to ensure safe drinking water, with no harm to waterconsumers and to the environment.
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