단결정 실리콘 태양전지의 후면 전극형성에 관한 비교분석

Abstract

Green Strategic Energy Research Institute, Sejong University, Seoul 143-747, Korea(Received May 17, 2010; Revised June 18, 2010; Accepted June 22, 2010)Abstract: Surface recombination loss should be reduced for high efficiency of solar cells. To reduce this loss, the BSF (back surface field) is used. The BSF on the back of the p-type wafer forms a p+layer, which prevents the activity of electrons of the p-area for the rear recombination. As a result, the leakage current is reduced and the rear-contact has a good Ohmic contact. Therefore, the open-circuit-voltage (Voc) and fill factor (FF) of solar cells are increased. This paper investigates the formation of the rear contact process by comparing aluminum-paste (Al-paste) with pure aluminum-metal(99.9%). Under the vacuum evaporation process, pure aluminum-metal(99.9%) provides high conductivity and low contact resistance of 4.2 mΩ㎝, but It is difficult to apply the standard industrial process to it because high vacuum is needed, and it's more expensive than the commercial equipment. On the other hand, using the Al-paste process by screen printing is simple for the formation of metal contact, and it is possible to produce the standard industrial process. However, Al-paste used in screen printing is lower than the conductivity of pure aluminum-metal(99.9) because of its mass glass frit. In this study, contact resistances were measured by a 4-point probe. The contact resistance of pure aluminum-metal was 4.2 mΩ㎝ and that of Al-paste was 35.69 mΩ㎝. Then the rear contact was analyzed by scanning electron microscope (SEM). Keywords: Rear contact, Back surface field (BSF), Rear recombination, Silicon solar cell, Al-paste