High quality CdS buffer layer developed via Zn salt additive engineering for Sb2S3 solar cells†

Antimony sulfide (Sb₂S₃) is regarded as a promising candidate for next-generation photovoltaic technology. In recent years, the efficiency of Sb₂S₃ solar cells has shown significant improvement, however, there still exists a considerable gap from the theoretical efficiency. This is partially due to the relatively high resistivity and parasitic light absorption of the CdS buffer layer, as well as the unsatisfactory crystal orientation of Sb₂S₃. In this work, a Zn salt additive is added to chemical bath solution of CdS to regulate the growth of CdS film. Elemental analysis indicates that only a small amount of zinc is deposited into the CdS film. The introduction of the Zn salt additive significantly increases the grain size and electrical conductivity of CdS, while also leading to preferential growth of the [hk1] orientation in Sb₂S₃ film. The low-cost Sb₂S₃ solar cells with inexpensive carbon electrodes were fabricated. The enhanced quality of the junction, attributed to the Zn salt additive, leads to improved charge transport and suppressed charge recombination in the Sb₂S₃ solar cells. As a result, the efficiency increases from 4.90% to 5.74%. This work presents a straightforward and efficient approach for the fabrication of superior CdS buffer layers and Sb₂S₃ solar cells.