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

SbS 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 SbS-based solar cells, here we control the defect in SbS 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 SbS so that the charge transport from SbS to the electron selection material becomes dynamically favorable. The introduction of ZnCl 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 SbS 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 SbS solar cells and among the top values in all kinds of SbS solar cells. This research provides a fundamental understanding regarding the properties of SbS and a convenient approach for enhancing the performance of SbS solar cells.