Open-circuit voltage (Voc) enhancement through integration of MoS2 layer at the interface between Mo and Sb2S3

In this work, Sb₂S₃ solar cells in a substrate configuration were fabricated using RF sputter-deposited Sb₂S₃ as the precursor layer. This deposition method remains relatively unexplored in antimony chalcogenide photovoltaic research. Our findings reveal that a double-layer structure can emerge during the crystallization of sputter-deposited precursors Sb₂S₃, resulting in morphological defects that are detrimental to the device’s overall performance. This double-layer structure is particularly pronounced in absorbers with a thickness of 1 µm or above and becomes indistinguishable in thinner layers. Furthermore, we examine the impact of incorporating a thin MoS² interfacial layer between the absorber and the back contact. This interfacial layer of MoS₂ significantly improves the open-circuit voltage (V_oc), reaching the highest value of 478 mV, compared to just 93 mV for devices without the MoS₂ layer. The MoS₂ also facilitates a preferred crystal orientation (hk1) of Sb₂S₃, improving charge collection efficiency. Using combined ultraviolet and X-ray photoelectron spectroscopy, we show that Mo is not suitable for Sb₂S₃ sputtered solar cells, and the valence band offset is significantly reduced in the presence of MoS₂. Our findings underscore the crucial role of the MoS₂ interfacial layer in improving device performance and optimizing the crystalline quality of Sb₂S₃ solar absorbers.