Analysis of PV Modules and N-type Silicon Solar Cells with Different Rear Metal Grid

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N-type silicon solar cells are being investigated due to the potential to obtain high efficiency. In this solar cell, the front p+ emitter is performed with boron doping and the Al or Al/Ag screen printing pastes don’t reach the development of Ag pastes used to form the front contact in n+pp+ solar cells. Moreover, the rear area covered by metal grid on the phosphorus back surface field may be optimized to increase the silicon solar cell efficiency and reduce the cost production. The goal of this paper is to present the analysis of PV modules and silicon solar cells developed on phosphorus-doped Czochralski wafers with different metal grid on the rear face. The solar cells were processed by using spin-on dopant to obtain the boron emitter and the back surface field was formed by phosphorus diffusion. The front metal grid was formed with Al/Ag paste and the rear area covered by the Ag metal paste was varied from 9% to 53%. Solar cells were manufactured, characterized and sorted taking into account the short-circuit current. Eight PV modules were fabricated using a standard process. Solar cells presented low fill factor. When the Ag/Sn/Cu ribbon was soldered on the front busbars of a solar cell, the fill factor rose from 0.70 to 0.75, causing an increase of 13.2% to 15.0% in the efficiency. Therefore, the fill factor of the PV modules was higher than that of solar cells. The reduction of the metal grid area on the rear face of solar cells did not affect the fill factor and solar cells with low rear metal coverage presented higher short-circuit current. The infrared thermography analysis was performed under a cloudless sky day with modules in the short-circuit condition. All modules presented hot spots and this result was not related to the different metallized rear area. The temperature difference between the solar cells of each photovoltaic module varied from 9°C to 18°C.