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.