Numerical simulations of multilevel impurity photovoltaic effect in the sulfur doped crystalline silicon

The multilevel impurity photovoltaic effect (IPV) of the sulfur doped crystalline silicon (c-Si) is studied by using the SCAPS program. The effects of impurity concentration (Nt) of two and four defect levels on the performance of sulfur doping c-Si solar cell are investigated, respectively. Then, the quantum efficiencies (QE) of different cases (without impurity, two and four defect levels) are considered. The results show that after the doping of sulfur, the infrared response of the c-Si solar cell is enhanced. Moreover, the infrared response wavelength range of the case considering two defect levels may be wider than that of four defect levels. In order to get the highest photovoltaic conversion efficiency (PCE), the number and the type of defect levels should be controlled. In the end, with four defect levels considered, the thickness and background doping concentration (ND for the n-type layer and Na for the p-type layer) of each layer of the n+-p-p+ structure are optimized. Our results suggest that higher PCE could be achieved than that without impurity by choosing a suitable doping concentration. The efficiency of 25.32% attained in the four-defect case improved the PCE by 2% more than the value of 23.22% without sulfur doping.