Study of the ion-implanted back-surface fields in front-contact front-junction solar cells

We have studied low energy ion-implanted P+ and N+ back surface field (BSF) layers with shallow junctions in front-contact front-junction solar cells for the first time as far as we know. With N+ BSF layer, V_oc and the efficiency of the solar cells increased on average by 30 mV and 1.3%, respectively. N+ BSF layer reduced recombination at the back surface significantly while P+ layer increased it. The higher V_oc due to the reduced recombination for the N+ BSF and the lower V_oc due to the increased recombination for the P+ BSF were attributed to the asymmetry in the capture cross-sections of the minority carriers (σ_n ~ 100*σ_p).