RISE: 21.5% Efficient Back Junction Silicon Solar Cell with Laser Technology as a Key Processing Tool

We employ laser technology as a key processing tool for fabricating our novel RISE (rear interdigitated single evaporation) silicon solar cells. The contactless production sequence incorporates a self-aligning single evaporation step for metallising the interdigitated rear contacts. In this paper, we compare in detail the performance of two types of RISE solar cells with different contact formations to the base: (a) back surface field formation via aluminium doping produced by local laser-firing of the aluminium contact (Al-BSF) and (b) local diffusion of boron (B-BSF). The best solar cell with B-BSF has an AM 1.5 efficiency of 21.5 %. The efficiencies of RISE solar cells with Al-BSF are considerably lower due to 5-10 % lower short-circuit currents. We ascribe these photocurrent losses to a less-efficient BSF effect of the laser-fired contact compared to a boron-diffused BSF