Copper doping of Sb₂S₃: fabrication, properties, and photovoltaic application

Sb₂S₃ solar cells are lagging behind conventional thin-film solar cells such as silicon solar cells and cadmium telluride solar cells in the power conversion efficiency (PCE). One of the most prominent problems is that the carrier concentration of Sb₂S₃ is relatively low. In order to increase the carrier concentration, elemental Cu was doped into Sb₂S₃ film by radio-frequency (RF) magnetron sputtering. We proved that Cu was doped into Sb₂S₃ films and mainly anchored with sulfur in the form of copper chalcogenide species at the surface and grain boundaries of Sb₂S₃. The doping of Cu essentially affects the physical and electrical properties of RF-sputtered Sb₂S₃ films such as the optical band gap, crystallinity, chemical composition, morphology, and carrier concentration. Specially, the electronic carrier concentration is remarkably increased from 6.28 × 10⁹ to 6.06 × 10¹⁰ cm⁻³ and the Fermi level is also significantly uplifted after prudent doping with Cu. Planar solar cells based on RF-sputtered Cu-doped Sb₂S₃ absorber deliver an increased PCE of 1.13% and show good stability. This research proves that doping of Cu is an alternative and effective way to improve the electronic property of Sb₂S₃ films and enhance the performance of Sb₂S₃ solar cells.