Investigation of RTP and belt fired screen printed AL-BSF on textured and planar back surfaces of silicon solar cells

Quality of screen printed (SP) Al-BSF on textured and planar back surfaces was assessed by fabricating and analyzing Si solar cells. BSF was formed by firing SP-Al in a conventional belt furnace as well as in an RTP system. I-V and IQE measurements revealed that the BSF formed on a textured surface by belt firing had the poorest quality. Belt BSF on the planar back resulted in 15 mV higher V/sub oc/. In contrast to the belt BSF, RTP BSF was superior and showed very small difference (<5 mV) between the flat and textured back cells. The positive effect of RTP is attributed to much higher temperature ramp-up rate which produces uniform Al melting and reduces the influence of surface condition. In contrast, slow ramp-up in belt produces non-uniform BSF even on a planar surface. This effect gets worse on textured surfaces.