Oxygen-Assisted Tailoring of Evaporated PbS Hole Transport Layer for Highly Efficient Antimony Sulfide Solar Cells

Antimony sulfide (Sb₂S₃) is regarded as one of the potential candidates for the next generation of photovoltaic absorber due to its excellent photoelectric properties. However, the selection and optimization of the hole transport layer (HTL) is still a major challenge for efficiency breakthrough of the Sb₂S₃ solar cells. In this work, lead sulfide (PbS) is deposited as a HTL of the Sb₂S₃ device by thermal evaporation for the first time. A high quality PbS films is conformally coated on the Sb₂S₃ rear surface by regulating the feeding amount, which thanks to the mass transfer mechanism of Ostwald ripening by scrutinizing the film growth kinetics. Meanwhile, both the valence band maximum (VBM) and Fermi levels are shifted down by a deliberate oxygen doping under a low vacuum ambient, which effectively reduces the offset between Sb₂S₃ and carbon electrode and then accelerates hole collection. Finally, it delivers an impressive photovoltaic conversion efficiency of 6.63% for carbon-based Sb₂S₃ solar cells, coupled with a V_oc of 779 mV, J_sc of 14.9 mA cm⁻² and FF of 57.13%, which is 13% higher than that under high vacuum condition.