26%-efficient and 2 cm narrow interdigitated back contact silicon solar cells with passivated slits on two edges

Abstract

Perimeter recombination is a relevant loss mechanism, in particular for cells with a large perimeter-to-area ratio and with poorly passivated edges, e.g., cut or cleaved solar cells for shingled modules. We experimentally demonstrate that cut edges can be well passivated during front-end processing. The resulting cells have an efficiency of 26%.The designated cell area of our lab-type highly efficient cells is smaller than the total area of the wafer. This causes recombination losses in the masked perimeter region. We separate the active cell area from the wafer on two sides of the cell by slits to reduce the transport of carriers into the perimeter region. We apply a diffusion model to describe impact of the slits on the perimeter recombination. The slits have an effective surface recombination velocity of down to 9 cm/s, depending on the resistivity of the base. For a base resistivity of 80 Ωcm, the average cell efficiency increases by 0.7 %abs as compared to embedded cells and by 2.3 %abs as compared to laser-cut cells due to the passivated slits.