β-FeSi₂ as the bottom absorber of triple-junction thin-film solar cells：A numerical study

Using β-FeSi₂ as the bottom absorber of triple-junction thin-film solar cells is investigated by a numerical method for widening the long-wave spectral response. The presented results show that the β-FeSi₂ subcell can contribute 0.273 V of open-circuit voltage to the a-Si/μc-Si/β-FeSi₂ triple-junction thin-film solar cell. The optimized absorber thicknesses for a-Si, μc-Si, and β-FeSi₂ subcells are 260 nm, 900 nm, and 40 nm, respectively. In addition, the temperature coefficient of the conversion efficiency of the a-Si/μc-Si/β-FeSi₂ cell is -0.308 %/K, whose absolute value is only greater than that of the a-Si subcell. This result indicates that the a-Si/μc-Si/β-FeSi₂ triple-junction solar cell has a good temperature coefficient. As a result, using β-FeSi₂ as the bottom absorber can improve the thin-film solar cell performance, and the a-Si/μc-Si/β-FeSi₂ triple-junction solar cell is a promising structure configuration for improving the solar cell efficiency.