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

• The MoS 2 layer acts as a seed layer for preferential growth in the (hk1) orientation of Sb 2 S 3 absorbers. • MoS 2 improves the band alignment and reduces V oc . • The thick 1 µm or above absorber forms a double layer and creates pin-holes. In this work, Sb 2 S 3 solar cells in a substrate configuration were fabricated using RF sputter-deposited Sb 2 S 3 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 Sb 2 S 3 , 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 MoS 2 interfacial layer between the absorber and the back contact. This interfacial layer of MoS 2 significantly improves the open-circuit voltage (V oc ), reaching the highest value of 478 mV, compared to just 93 mV for devices without the MoS 2 layer. The MoS 2 also facilitates a preferred crystal orientation (hk1) of Sb 2 S 3 , improving charge collection efficiency. Using combined ultraviolet and X-ray photoelectron spectroscopy, we show that Mo is not suitable for Sb 2 S 3 sputtered solar cells, and the valence band offset is significantly reduced in the presence of MoS 2 . Our findings underscore the crucial role of the MoS 2 interfacial layer in improving device performance and optimizing the crystalline quality of Sb 2 S 3 solar absorbers.