Contact resistance of local rear side contacts of screen-printed silicon PERC solar cells with efficiencies up to 19.4%

Summary form only given. We demonstrate industrially feasible large-area solar cells with passivated homogenous emitter and rear achieving energy conversion efficiencies of up to 19.4 % on 125×125 mm² p-type 2-3 Ωcm boron-doped Czochralski silicon wafers. Front and rear metal contacts are fabricated by screen-printing of silver and aluminum paste and firing in a conventional belt furnace. We implement three different dielectric rear surface passivation stacks. The dielectrics at the rear result in a decreased surface recombination velocity of down to S_rear = 70 cm/s, and an increased internal IR reflectance of up to 91 % corresponding to an improved J_sc of up to 38.9 mA/cm². We observe an increase in cell efficiency from 18.7 % for the best full-area Al-BSF reference cell up to 19.4 % for the PERC solar cell. To our knowledge, the energy conversion efficiency of 19.4 % is the best value reported so far for large area screen-printed solar cells. However, these cells suffer from a moderate fill factor below 76 % due to an increased series resistance. We investigate different rear metallization fractions by varying the pitch and the width of the local line contacts. The solar cell analysis reveals a significant contribution of the local rear contacts to the total series resistance. By fitting of the experimental data with an analytical model we deduce a specific contact resistance of screen-printed local aluminum rear contacts of (55 ± 10) m Ωcm².