Industrially feasible all side passivated silicon based C-MWT concentrator solar cells

Starting from the conventional silicon solar cell that features a single diffused shallow emitter and screen-printed contacts on both sides, we discuss possible ways to extend one- and multiple-sun conversion efficiency. From this perspective, the metal wrap through (MWT) concept that also features a full area aluminum back surface field (BSF) is discussed. By combining the passivated emitter and rear cell (PERC) approach with the MWT concept into a MWT-PERC concept, we achieve a one-sun conversion efficiency of 20.2%. Also discussed are improvements in selected process steps. By retaining the conventional Al-BSF cell design but switching to a two step metallization approach of the front, while adding a thermal treatment after emitter formation, we achieve an independently confirmed one-sun conversion efficiency of 20.1%. Adding the PERC approach to that superior front side, a one-sun conversion efficiency of 20.5% is demonstrated, which also has been independently confirmed. Under concentration, highly illuminated solar cells profit more from improvements of the rear side where most of the series resistance r_s is generated. As a consequence, on a solar cell that features a full area Al-BSF we achieve the highest conversion efficiency of 20.4% under 15 fold concentration and 19.1% at 50 suns. By excluding the busbar area the conversion efficiency increases to 20.9% and 19.5% respectively.