n-Type Doping of Sb2S3 Light-Harvesting Films Enabling High-Efficiency Planar Heterojunction Solar Cells

Sb₂S₃ is a kind of new light-absorbing material possessing high stability in ambient environment, high absorption coefficient in the visible range, and abundant elemental storage. To improve the power conversion efficiency of Sb₂S₃-based solar cells, here we control the defect in Sb₂S₃ absorber films. It is found that the increase of sulfur vacancy is able to upgrade photovoltaic properties. With the increase in sulfur vacancy, the carrier concentrations are increased. This n-type doping gives rise to an upshift of the Fermi level of Sb₂S₃ so that the charge transport from Sb₂S₃ to the electron selection material becomes dynamically favorable. The introduction of ZnCl₂ in film fabrication is also found to regulate the film growth for enhanced crystallinity. Finally, the photovoltaic parameters, short-circuit current density, open-circuit voltage, and the fill factor of the device based on the Sb₂S₃ film are all considerably enhanced, boosting the final power conversion efficiency from 5.15 to 6.35%. This efficiency is the highest value in planar heterojunction Sb₂S₃ solar cells and among the top values in all kinds of Sb₂S₃ solar cells. This research provides a fundamental understanding regarding the properties of Sb₂S₃ and a convenient approach for enhancing the performance of Sb₂S₃ solar cells.