Summary of Patented Technology of Buried Grid Solar Cells

Summary of Patented Technology of Buried Grid Solar Cells

Abstract: With the continuous development and improvement of traditional screen printing technology, an industrialized high-efficiency battery-buried-gate battery has also achieved great development and improvement of buried-gate solar batterys as the currently widely used solar battery type. It plays a decisive role in conversion efficiency and industrial production. Based on the premise of buried-gate battery as the main research object, this paper mainly analyzes the development status and research direction of buried-gate solar batterys, and the strategic layout of such solar batterys in important enterprises in the field of solar energy.
【Keywords】 Patent application for buried-gate solar batterys

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1 Basic structure of buried-gate batteries
The grid battery has also achieved great development and improvement. More specifically, the front contact of the battery is typically deposited as an open gate pattern to allow light to be absorbed by the exposed silicon substrate, while the front gate is deposited in the buried recess to reduce gate shadow loss ( Grid-shading loss, this type of solar battery is commonly referred to as a Buried Contact solar battery (also known as a laser-grooved buried gate-LGBG solar battery), referred to as a buried-gate battery. The reasons for the high efficiency of the buried gate battery include: because the metal gate line has better conductivity and the contact resistance with the re-diffusion region in the trench is smaller, the fill factor is higher. At the same time, since the surface shading area is relatively small, the current is relatively high for a large-area battery. In addition, the process itself can produce considerable gettering during the process.
2 Technical development route of buried gate battery

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It is precisely because of the superiority of buried-gate battery, its technical development route also has the following aspects: (1) Improvement of buried gate structure, mainly for grid Improvement of the groove manufacturing process, including laser groove and mechanical groove; (2) improvement of battery efficiency, mainly including reduction of surface shading area, process improvement of battery reflective film or optimization of metal electrode of buried gate structure, etc. (3) From the industrialization point of view, focus on manufacturing process improvements that reduce production costs, such as improvements in electroless nickel/copper/silver plating methods.

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3 The technical development route of important applicants for buried grid batterys
The large-scale manufacturing technology and equipment of crystalline silicon solar batterys based on screen printing technology have been significantly improved, and many companies have invested in the industry of buried-gate battery technology. In the chemical manufacturing industry, these companies mainly include BP Solar, Telefunken and Samsung. Among them, BP Solar and Samsung have successfully used buried-gate battery technology to produce large-scale commercial batteries. The patent applications of the above two companies are sorted out from the perspective of the development process of buried-gate battery technology, and the development status and trend of buried-gate battery technology are as follows:
First, BP Solar proposed to the University of New South Wales. The prototype of the buried-gate battery has been improved (see WO02103810A1), and a relatively complete and mature buried-gate battery structure is proposed, and the back surface field is applied to the silicon solar battery, thereby completing the low-cost requirements and the optimization of the manufacturing process in industrial production; BP Solar has proposed a process to improve the metallization coating (see EP1936698A1), using silicon nitride instead of silicon oxide as an anti-reflection film to improve the light reflectivity of the buried-gate battery; in addition, it is buried for the University of New South Wales. In the method of grid batterys, BP Solar proposes a method of forming elongated grooves on a silicon substrate and intersecting the contact finger system to form a conductive front contact (see EP 1892767 A1), which avoids metallization in front of screen printing. Formation of ohmic contact under undesired areas, while firing the front metallized pattern of screen printing LPCVD deposition member and the conditions were optimized; BP Solar Corporation addition to the improvement of the manufacturing process and the buried gate battery structure outside the company also relates to a solar battery manufacturing equipment, research and development of the production line.
\u003c There are relatively many patent applications in terms of battery structure and related equipment. According to the technical development and improvement of the above-mentioned buried-gate battery, the company's patent application is as follows:

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First, Samsung proposed a buried-gate solar battery with a back contact electrode structure based on the buried-gate battery proposed by the University of New South Wales (BCSC). ) (see KR97054567A1), and proposes to use a lower cost and larger oxide layer to cover the upper surface of the silicon dioxide to improve the reflection efficiency of the battery; then, Samsung has proposed a buried-gate solar battery ( A partial P+ diffusion layer is formed on the silicon substrate of BCSC) (see KR97018751A), and the diffusion layer has a flat upper surface to have higher battery conversion efficiency; after that, Samsung proposes to improve the P-type doping on the back side of the buried-gate solar battery. The process (see KR97030930A), specifically doping with boron element, can further improve the conversion efficiency of the battery; further, Samsung proposes to form a reverse layer between the surface of the silicon substrate and the oxide layer (see KR98020311), Thereby increasing the fill factor and conversion efficiency of the buried gate battery; then, Samsung The company proposes to use an annealing step to form the oxide layer of the buried gate battery (see KR98083153A), which simplifies the manufacturing process of the buried gate battery and reduces the production cost. Then, Samsung also proposed a buried gate electrode. Method (see KR20050023181A), which can reduce the steps of high temperature sintering in previous manufacturing processes, further reducing production costs. In addition, in addition to the simplification of the buried gate battery manufacturing process and the reduction of production cost and the improvement of the structure of the buried gate battery, Samsung has also proposed a number of related patent applications for manufacturing devices and process conditions.
Through the combing of the patent applications of the two companies on the buried grid battery, it can be found that the company mainly focuses on the reduction of production cost when the product is industrialized. However, the buried grid battery can be further developed in the industry. For applications, from crystalline silicon batterys as a substitute for traditional energy sources, and from the perspective of better benefiting human life, buried-gate batteries still need further development, for example, by plasma chemical vapor deposition (PECVD). The silicon nitride film (SiN) is used as the anti-reflection film on the front surface of the battery; the silver paste is modified to achieve better ohmic contact in the case where the sheet resistance of the surface of the battery is increased; co-firing technology; And use a fine screen to reduce the width of the grid line; in the laser engraving method, it is necessary to develop a multi-beam laser grooving device to improve the production efficiency; the improvement of the industrial production equipment and the optimization of the process conditions in the mechanical grooving method, etc. Adapt to the requirements of industrial technology.
4 Conclusion

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Based on the current published invention patent application and the application volume, application direction and application content layout of important applicants in this field, this paper briefly describes the development and improvement of buried gate battery in solar battery. This paper focuses on the advantages and research directions of buried-gate batteries compared with traditional screen-printed batteries. At the same time, it analyzes the status quo of patent applications and patent strategic layouts of important enterprises in the field of intellectual property patents. The new energy source of green energy can develop better and live in harmony with human beings.

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