Simulation of High Efficiency Heterojunction Solar Cells with AFORS-HET

In this paper, the high efficiency TCO/a-Si:H (n)/a-Si:H(i)/c-Si(p)/uc-Si(p+)/Al HIT (heterojunction with intrinsic thin-layer) solar cells was analyzed and designed by AFORS-HET software. The influences of emitter, intrinsic layer and back surface field (BSF) on the photovoltaic characteristics of solar cell were discussed. The simulation results show that the key role of the intrinsic layer inserted between the a-Si:H and crystalline silicon substrate is to decrease the interface states density. If the interface states density is lower than 1010cm-2V-1 thinner intrinsic layer is better than thicker one. The increase of the thickness of the emitter will decrease the short-current density and affect the conversion efficiency. Microcrystalline BSF can increase conversion efficiency more than 2 percentage points compared with HIT solar cell with no BSF. But this BSF requires the doping concentration must exceed 1020cm-3. Considered the band mismatch between crystalline silicon and microcrystalline silicon, the optimal band gap of microcrystalline silicon BSF is about 1.4-1.6eV.