Control of electrical potential distribution for efficient electron transport in Sb₂Se₃ solar cells

Despite the promising intrinsic properties of antimony selenide (Sb₂Se₃) as a photovoltaic absorber, interfacial control of the device is necessary to overcome current plateau of efficiency. Herein, we suggest that smooth flow of charge carriers with adjusted structural and electrical properties could be achieved by inserting appropriate bifacial interlayers. The back interface of Mo/Sb₂Se₃ was modified by inserting an MoSe₂ interlayer, which was formed by selenizing Mo. Formation of the 1-dimensional nanorod arrays of Sb₂Se₃ deposited on MoSe₂ was confirmed through increase of the textured coefficient in (hk1) orientation, which are beneficial for carrier transport. The cross-sectional potential distribution between Mo/Sb₂Se₃ and Mo/MoSe₂/Sb₂Se₃ was compared, and the results suggest that the energy barrier for electrons was formed by MoSe₂, efficiently blocking electrons while extracting holes to the hole transport layer. These results further supported by enhanced vertical current flow throughout the absorber. However, irregular formation of p-n junction caused by rough rod structure of Sb₂Se₃ could limit the short-circuit current. A SnO_x layer deposited using atomic layer deposition on Sb₂Se₃ helps to form a uniform p-n junction, reducing potential fluctuations at CdS and lessen redundant charge flow in the lateral direction. The shift of fermi level of CdS towards the conduction band minimum further supports increased electron flows across the junction.