Star-shaped boroxine-linked fluorinated dopant for Spiro-OMeTAD enables high performance perovskite solar cells

The hygroscopic nature and severe ions diffusion of conventional dopant Li-TFSI, along with interfacial ionic defects, limiting the efficiency and stability of n-i-p perovskite solar cells (PSCs). To address this, we propose a single-dopant strategy employing a multifunctional, star-shaped dopant 2,4,6-tris(3,4,5-trifluorophenyl)boroxine (TBRX) with a Lewis acidic boroxine core and highly electronegative fluorinated aryl groups, incorporated into Spiro-OMeTAD. Theoretical and experimental results indicate that TBRX significantly enhances hole mobility, conductivity and the flatness of hole-transporting layer (HTL) while passivating interfacial defects (Pb2+, VI), leading to a reinforced perovskite/HTL interface. Additionally, the corresponding p-dopant effectively reduces the energy barrier between the perovskite and the HTL, promoting efficient hole extraction. Consequently, Spiro-OMeTAD:TBRX-based devices deliver a high PCE of 25.57 % (certified at 25.01 %) with excellent long-term operational stability obtained for over 1000 h, retaining ∼94 % of its initial efficiency after 1000 h according to ISOS-L-2 protocols, highlighting the significance of utilizing multifunctional single-dopant framework.