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 (Rop) to obtain the maximal solar cell efficiency is relative to the bulk defect density, such as oxygen defect density (Dod), in the substrate and the interface defect density (Dit) on the interface of amorphous/crystalline Si heterojunction. The larger Dod or Dit is, the higher Rop is. The effect of Dit is more obvious. Rop is about 0.5 Ω cm for Dit = 1.0 × 1011/cm2, but is higher than 1.0 Ω cm for Dit = 1.0 × 1012/cm2. In order to obtain very excellent solar cell performance, Si substrate, with the resistivity of 0.5 Ω cm, Dod lower than 1.0 × 1010/cm3, and Dit lower than 1.0 × 1011/cm2, is preferred, which is different to the traditional opinion that 1.0 Ω cm resistivity is the best.