Which can help me get a "on the solar cell preparation process" in English and Chinese information, as long as a paragraph of the production can be!

As we all know, the use of solar energy has many advantages, photovoltaic power generation will provide mankind with the main source of energy, but at present, in order to make solar power with a large market, accepted by the majority of consumers, improve the photoelectric conversion efficiency of solar cells, reduce production costs should be the biggest goal we pursue, from the current development of the international solar cell development process can be seen in the development trend of monocrystalline silicon, polycrystalline silicon, banded silicon, thin film materials (including microcrystalline silicon based film, compound-based film, and compound-based film, and the production of solar cells) The development trend of international solar cells can be seen as monocrystalline silicon, polycrystalline silicon, ribbon silicon, thin film materials (including microcrystalline silicon-based film, compound-based film and dye film). From the industrialization of the development point of view, the center of gravity has been from monocrystalline to polycrystalline direction, the main reasons are; [1] can supply the solar cell of the head and tail of the material is getting less and less; [2] for solar cells, square substrate is more cost-effective, through the casting method and the direct solidification method of polysilicon can be obtained directly from the square material; [3] polycrystalline silicon production process continues to make progress, the fully automated casting furnace each production cycle (50 hours) can produce more than 200 kg of silicon ingots, the size of the grain to the centimeter level; [4] due to the rapid research and development of monocrystalline silicon process in the last decade, in which the process is also applied to the production of polysilicon cells, such as selective corrosion emission junction, back surface field, corrosion of velvet, surface and body passivation, fine metal gate electrodes, the use of screen-printing technology can be used to make the gate electrode width is reduced to 50 microns, the height reaches 15 Micron above, fast thermal annealing technology for the production of polycrystalline silicon can greatly reduce the process time, a single piece of thermal process time can be completed within one minute, using the process in 100 square centimeters of polycrystalline silicon wafers made on the battery conversion efficiency of more than 14%. Reportedly, the current 50 ~ 60 micron polycrystalline silicon substrate made on the battery efficiency of more than 16%. The use of mechanical grooving, screen printing technology in 100 square centimeters of polycrystalline efficiency of more than 17%, no mechanical grooving in the same area efficiency of 16%, the use of buried grid structure, mechanical grooving in 130 square centimeters of polycrystalline battery efficiency reached 15.8%. The following two aspects of the polycrystalline silicon cell process technology is discussed.

2. Laboratory high-efficiency cell processes Laboratory technologies usually do not consider the cost of cell fabrication and whether they can be mass-produced, but simply study the ways and means to achieve the highest efficiency, providing the limits of what can be achieved with specific materials and processes. 2.1 On light absorption For light absorption, the main approaches are to (1) reduce the surface reflectance; (2) change the path of the light in the body of the cell; and (3) use the backside reflection. For monocrystalline silicon, the application of anisotropic chemical corrosion can be made on the (100) surface of the pyramidal velvet structure to reduce the surface light reflection. However, polysilicon crystal direction deviation (100) surface, using the above method can not make a uniform velvet surface, the following methods are currently used: [1] laser grooving laser grooving method can be used in the polysilicon surface to produce inverted pyramid structure, in the spectral range of 500 ~ 900nm, the reflectivity of 4 ~ 6%, and the surface of the production of double-layer reflectance reduction film is comparable. While in the (100) surface monocrystalline silicon chemical production of velvet reflectivity of 11%. Laser production of velvet than in the smooth surface plating of double-layer reflection-reducing film layer (ZnS/MgF2) battery short-circuit current to increase by about 4%, which is mainly long-wave light (wavelengths greater than 800nm) into the cell diagonal reasons. The problem with laser-made velvet is that in the etching, the surface is damaged and some impurities are introduced, and the damaged surface layer has to be removed by chemical treatment. The solar cell made by this method usually has a high short-circuit current, but the open-circuit voltage is not too high, the main reason is that the surface area of the cell is increased, causing the compound current to increase. [2] chemical groove Application of mask (Si3N4 or SiO2) isotropic corrosion, the corrosion solution can be acidic corrosion solution, can also be a higher concentration of sodium hydroxide or potassium hydroxide solution, the method can not be formed by anisotropic corrosion of the kind of sharp cone-shaped structure. It has been reported that the velvet surface formed by this method has obvious anti-reflective effect on the spectral range of 700 to 1030 microns. However, the mask layer generally has to be formed at higher temperatures, causing a decline in the performance of polysilicon materials, especially for lower quality polycrystalline materials, and a shorter oligon lifetime. Application of this process in 225cm2 of polycrystalline silicon made on the cell's conversion efficiency reached 16.4%. The mask layer can also be formed by screen printing. [3] Reactive Ion Etching (RIE) This method is a maskless etching process, and the fluff formed is particularly low in reflectivity, which can be less than 2% in the spectral range of 450 to 1000 micrometers. It is an ideal method from the optical point of view only, but the problem is that the silicon surface is severely damaged, and the open-circuit voltage and fill factor of the cell appear to decrease. [4] Fabrication of reflection-reducing film layer For high-efficiency solar cells, the most common and effective method is to vaporize ZnS/MgF2 double-layer reflection-reducing film, and its optimal thickness depends on the thickness of the oxide layer below and the characteristics of the cell surface, for example, whether the surface is smooth or velvet, reflection-reducing processes are also available for vaporizing Ta2O5, PECVD deposition of Si3N3, etc. ZnO conductive film can also be used as a reflection-reducing material. 2.2 Metallization technology In the fabrication of high-efficiency batteries, the metallization electrode must match the design parameters of the battery, such as surface doping concentration, PN junction depth, and metal material. Laboratory batteries are generally small (area less than 4cm2), so fine metal grid lines (less than 10 microns) are required, and the methods generally used are photolithography, electron beam evaporation, and electron plating. Plating processes are also used in industrialized mass production, but evaporation and lithography are not low-cost process technologies when used in combination. [1] Electron beam evaporation and electroplating Usually, the application of positive gel stripping process, evaporation of Ti / Pa / Ag multilayer metal electrodes, to reduce the series resistance caused by the metal electrodes, often need to be a relatively thick layer of metal (8 to 10 microns). The disadvantage is that the electron beam evaporation caused by the silicon surface/passivation layer interface damage, so that the surface composite to improve the process, therefore, the process, using a short period of time to evaporate the Ti/Pa layer, in the evaporation of the silver layer of the process. Another problem is that when the contact surface between metal and silicon is large, it will definitely lead to an increase in the rate of oligo compounding. Process, the use of tunnel junction contact method, in the silicon and metal into a thin oxide layer between the formation (general thickness of about 20 microns) the application of lower work function of the metal (such as titanium, etc.) can be induced on the surface of the silicon a stable layer of electron accumulation (can also be introduced to deepen the anti-type of fixed positive charge). Another method is to open a small window (less than 2 microns) on the passivation layer, and then precipitate a wider metal gate line (usually 10 microns), forming a mushroom-like electrode, with this method in the 4cm2 Mc-Si on the cell's conversion efficiency reached 17.3%. At present, in the mechanical groove surface also used Shallow angle (oblique) technology. 2.3 PN junction formation technology [1] Emissive region formation and phosphorus absorption For high-efficiency solar cells, the formation of the emissive region is generally used to selective diffusion, the formation of the metal electrode below the heavy impurity region and in the electrode between the realization of the shallow concentration of the diffusion of the emissive region of the shallow concentration of the diffusion of the cell to enhance the response to blue light, but also to make the silicon cell conversion efficiency of 17.3%. Shallow concentration diffusion in the emissive region enhances the cell's response to blue light and makes the silicon surface easy to passivate. Diffusion methods include two-step diffusion process, diffusion plus corrosion process and buried diffusion process. At present, using selective diffusion, the conversion efficiency of 15×15cm2 cell reaches 16.4%, and the surface square resistance in the n++ and n+ regions is 20Ω and 80Ω, respectively. For Mc-Si materials, the effect of diffusion phosphorus adsorption on the cell has been widely studied, and a longer phosphorus adsorption process (generally 3 to 4 hours) can make some Mc -Si oligon diffusion lengths by two orders of magnitude. In the study on the effect of substrate concentration on the absorption, it is found that even for high concentration of substrate materials, the absorption can also obtain a larger oligon diffusion length (greater than 200 μm), and the open-circuit voltage of the cell is greater than 638 mv, and the conversion efficiency is more than 17%. [2] Formation of back surface field and aluminum absorption technology In Mc-Si cells, the back p + p junction is formed by uniform diffusion of aluminum or boron, boron source is generally BN, BBr, APCVD SiO2: B2O8, etc., aluminum diffusion for evaporation or screen printing of aluminum, sintered at 800 degrees Celsius completed, the role of aluminum absorption has also carried out a large number of studies, and the role of aluminum absorption, with the phosphorus diffusion of impurity absorption. Unlike phosphorus diffusion impurity absorption, aluminum impurity absorption is carried out at relatively low temperatures. Its medium defects are also involved in the dissolution and deposition of impurities, and at higher temperatures, the deposited impurities are easy to dissolve into the silicon, which adversely affects Mc-Si. To date, the regional backfield has been used in monocrystalline silicon cell process, but in polycrystalline silicon, or the application of all-aluminum back surface field structure. [3] Bifacial Mc-Si cells Mc-Si bifacial cells have a conventional structure on the front side, and the back side is a structure in which N+ and P+ cross each other, so that photogenerated oligons generated by frontal illumination but located in the vicinity of the back side can be absorbed efficiently by the back electrode. The back electrode acts as an effective complement to the frontal electrode, and also acts as an independent planted current collector for the backside illumination and scattered light, with a reported conversion efficiency of more than 19% under AM1.5.2.4 Surface and body passivation techniques For Mc-Si, the presence of high grain boundaries, point defects (vacancies, gap-filling atoms, metal impurities, oxygen, nitrogen, and Their complexes) on the surface of the material and in vivo defects of the passivation is particularly important, in addition to the previously mentioned absorption technology, passivation process has a variety of methods, through thermal oxidation to make the silicon suspension bond saturation is a more commonly used method to make the Si-SiO2 interface of the composite speed is greatly reduced, and the effect of its passivation depends on the surface concentration of the emission zone, the density of interfacial states and the electron, hole levitation cross-section. Annealing in hydrogen atmosphere can make the passivation effect more obvious. The use of PECVD precipitation of silicon nitride has recently been very effective on the front side because of the effect of hydrogenation during film formation. The process can also be applied in large-scale production. The application of Remote PECVD Si3N4 can make the surface compounding speed is less than 20cm/s.

3 Industrialized battery process Solar cell from the research laboratory to the factory, experimental research towards large-scale production is the path of its development, so to be able to achieve the characteristics of industrialized production should be: [1] the battery production process to meet the assembly line operation; [2] to be able to large-scale, modernized production; [3] to achieve high efficiency and low cost. Of course, the main goal is to reduce the production cost of solar cells. At present, the main development direction of polycrystalline silicon cells toward large area, thin substrate. For example, 125 × 125mm2, 150 × 150mm2 or even larger scale monolithic cells can be found on the market, and the thickness has been reduced from the original 300 microns to the current 250, 200 and 200 microns or less. Efficiency has been greatly improved. Japan's Kyomagnetic (Kyocera) company 150 × 150 of the battery small batch production of photoelectric conversion efficiency of 17.1%, the company's production volume in 1998 reached 25.4MW. (1) screen printing and its related technologies Polycrystalline silicon battery scale production in the extensive use of the screen printing process, which can be used for the diffusion of the source of the printing, the front side of the metal electrodes, the back of the contact electrodes, the Reduced reflection film layer, etc. With the improvement of screen materials and process level, screen printing process will be more commonly used in the production of solar cells. a. Formation of the emissive region Use screen printing to form PN junction, instead of the conventional tube furnace diffusion process. Generally in the polysilicon front side of the printing of phosphorus-containing paste, in the reverse side of the printing of aluminum-containing metal paste. After printing, diffusion can be completed in a mesh belt furnace (usually at 900 degrees Celsius), so that printing, drying, and diffusion can form a continuous production. Screen printing diffusion technology formed by the emissive zone is usually higher surface concentration, then the surface photogenerated carrier complex is larger, in order to overcome this shortcoming, the process uses the following selection of the emissive zone process technology, so that the conversion efficiency of the battery has been further improved. b. Selective Emission Zone Process In the diffusion process of polysilicon cells, selective emission zone technology is divided into localized corrosion or two-step diffusion method. Localized corrosion is the use of dry (such as reactive ion corrosion) or chemical corrosion method, the heavy diffusion layer in the area between the metal electrodes corroded off. Initially, Solarex applied the reactive ion etching method in the same equipment, first using high reactive power to etch away the heavy dopant layer between the metal electrodes, and then using low power to deposit a thin film of silicon nitride, which plays the dual role of anti-reflection and cell surface passivation. A cell with a conversion efficiency of more than 13% was made on a 100cm2 polycrystalline. In the same area, the application of two diffusion method, without mechanical velvet surface of the conversion efficiency of 16%. c. The formation of the back surface field back PN junction is usually formed by screen printing A paste and thermal annealing in a mesh belt furnace, the process in the formation of the back surface of the junction at the same time, the impurities in the polysilicon has a good suction effect, aluminum suction process is generally completed in the high temperature section, measurements show that suction effect can be made in the previous high-temperature process caused by the polysilicon oligo-lifetime of the decline in the recovery. Good back surface field can significantly improve the open-circuit voltage of the cell. d. Screen printing metal electrodes in large-scale production, screen printing process and vacuum evaporation, metal plating and other processes, compared with the advantages of the current process, the front side of the printed material is generally used in the selection of silver-containing paste, the main reason is that silver has a good electrical conductivity, solderability and low diffusion properties in the silicon. Screen printing, annealing of the metal layer formed by the conductivity depends on the chemical composition of the paste, the content of the vitreous humor, screen roughness, sintering conditions and the thickness of the screen plate. In the early eighties, screen printing has a number of defects, i) such as grid line width is larger, usually greater than 150 microns; ii) resulting in greater shading, the cell filling factor is lower; iii) is not suitable for surface passivation, mainly surface diffusion of higher concentrations, otherwise the contact resistance is larger. Currently with advanced methods can screen print the grid line with line width up to 50 microns, thickness more than 15 microns, square resistance of 2.5~4mΩ, this parameter can meet the requirements of high-efficiency batteries. Some people in the 15 × 15 cm2 Mc-Si on the screen-printed electrodes and evaporated electrodes made by the solar cell comparison, the parameters are almost no difference.4 Conclusion Polycrystalline silicon battery production process continues to move forward to ensure that the efficiency of the battery continues to improve, the cost of the battery is reduced, with the deepening of the understanding of the material, device physical and optical properties, resulting in battery With the deepening of the understanding of the physical and optical properties of the materials and devices, resulting in a more reasonable structure of the cell, the distance between the laboratory level and industrialized mass production is constantly shrinking. Screen printing and buried grid process for high-efficiency, low-cost batteries play a major role in high-efficiency Mc-Si battery components have entered the market in large quantities, the current research is being committed to the new nature of the thin film structure, inexpensive substrate on the battery, etc., in the face of the user, we need to do the work is to achieve a larger volume, low-cost production, may we work harder to achieve this goal.