Semiconducting β-FeSi2 thin film with high absorption coefficient has been recognized as a novel solar cell material. In this study, the photovoltaic properties of n-β-FeSi2/p-Si and p-β-FeSi2/n-Si heterojunction solar cells with varying band offsets and doping concentrations are analyzed using numerical methods. Calculated results show that changes in electron affinity and doping concentration affect the photovoltaic properties of β-FeSi2/Si heterojunctions. Two types of effect can be seen in spike-like band offset, depending on the doping concentrations of β-FeSi2 and Si. Calculated results can be explained by the band diagrams and photo-generated carrier collections of β-FeSi2/Si heterojunctions. To avoid decreased conversion efficiency, low doping concentration of β-FeSi2 and high doping concentration of Si are favorable. The results of this study can serve as a guide in fabricating β-FeSi2/Si heterojunction solar cells. Copyright © 2014 John Wiley & Sons, Ltd.