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Tham khảo tài liệu 'solar energy 2012 part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Contact Definition in Industrial Silicon Solar Cells 383 Fig. 5. Components of the cell s series resistance equivalent circuit for an Aluminium bsf solar cell are shown inside the dashed box Considering that current is extracted from the soldered points that join the bus bar with the interconnection conductive ribbons tabs and these points are homogeneously distributed along the bus bar it is possible to define a basic unitary cell and the number of them that are needed to get the total series resistance being each soldered point in contact with four unitary cells as it is shown in Fig. 6. Fig. 6. Basic calculus cell for two bus-bar it is shown the basic unitary cell size for the case of having two collecting bus-bars with a variable number of bonding points per bus-bar in the solar cell The higher the number of soldered points per bus-bar the more accurate the result of this simple modelling because in that way the real current flow in an interconnected solar cell produces a natural distribution of the device in regions that are more similar to the basic cell proposed by this modelling. Components of the unitary basic cell s series resistance are detailed in Table 3 expressions such as the emitter finger and bus components are deduced from matching the power loss integrated along the current path increasing the current along this path with the power loss associated to an equivalent resistance crossed by the total current ITotal2 Requivalent . It must be noted that series resistance associated to the BSF layer has been neglected due to its low value. Equations that are summarized in Table 3 include characteristic parameters from the different materials such as Pbase bulk resistivity of the wafer Pmetal RprontPaste and RBackPaste resistivity of the metallic grid in Qcm and semiconductor-metal contact specific resistivities in Qcm2 characteristic parameters from the process and wafer such as Re Emitter layer resistance in Q square L wafer side and wtale base width .