Optimized resistivity of p-type Si substrate for HIT solar cell with Al back surface field by computer simulation

For HIT (heterojunction with intrinsic thin-layer) solar cell with Al back surface field on p-type Si substrate, the impacts of substrate resistivity on the solar cell performance were investigated by utilizing AFORS-HET software as a numerical computer simulation tool. The results show that the optimized substrate resistivity (R_op) to obtain the maximal solar cell efficiency is relative to the bulk defect density, such as oxygen defect density (D_od), in the substrate and the interface defect density (D_it) on the interface of amorphous/crystalline Si heterojunction. The larger D_od or D_it is, the higher R_op is. The effect of D_it is more obvious. R_op is about 0.5 Ω cm for D_it = 1.0 × 10¹¹/cm², but is higher than 1.0 Ω cm for D_it = 1.0 × 10¹²/cm². In order to obtain very excellent solar cell performance, Si substrate, with the resistivity of 0.5 Ω cm, D_od lower than 1.0 × 10¹⁰/cm³, and D_it lower than 1.0 × 10¹¹/cm², is preferred, which is different to the traditional opinion that 1.0 Ω cm resistivity is the best.