Spiro‐OMeTAD:Sb₂S₃ Hole Transport Layer with Triple Functions of Overcoming Lithium Salt Aggregation, Long‐Term High Conductivity, and Defect Passivation for Perovskite Solar Cells

The development of a hole transport layer (HTL) with persistent high conductivity, good moisture/oxygen barrier ability, and suitable passivation ability of perovskite defects is very important for achieving high power conversion efficiency (PCE) and long‐term stability of perovskite solar cells (PSCs). However, the state‐of‐the art HTL, lithium bis(trifluoromethanesulfonyl)‐imide (Li‐TFSI)‐doped 2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐OMeTAD), does not have these abilities. Herein, the incorporation of antimony sulfide (Sb₂S₃) nanoparticles as a multifunctional additive into spiro‐OMeTAD is demonstrated. The Sb₂S₃ effectively improve the compactness of composite spiro‐OMeTAD:Sb₂S₃ HTL by inhibiting the Li‐TFSI aggregation and effectively prevent the infiltration of moisture and oxygen into the perovskite layer, resulting in its high chemical stability. More importantly, Sb₂S₃ not only improves the conductivity and hole mobility of the spiro‐OMeTAD:Sb₂S₃ through the oxidation of spiro‐OMeTAD by Sb₂S₃, but also makes the high conductivity more durable and stable in the atmospheric environment. In addition, Sb₂S₃ also effectively passivates the perovskite defects and accelerates the charge transfer from perovskite layer to HTL. As a consequence, the optimized PSCs based on spiro‐OMeTAD:Sb₂S₃ HTL exhibit a much higher PCE (22.13%) than that (19.29%) of the PSCs without Sb₂S₃ and show a greatly improved stability.