Improved Power Conversion Efficiency and Stability of Perovskite Solar Cells Induced by Surface Modification with Multifunctional Dipoles

Perovskite solar cells (PSCs) have garnered widespread attention owing to their outstanding power conversion efficiencies (PCEs), which currently exceed 27%. Good interfacial contact and energy level alignment between the perovskite layer and the hole transport layer (HTL) are essential for efficient charge-carrier collection and nonradiative recombination minimization. Spiro-OMeTAD is commonly employed as the HTL in high-performance planar PSCs. Because of its intrinsically low hole mobility, spiro-OMeTAD is frequently doped with the p-type additive lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) to increase electrical conductivity. However, the pronounced hygroscopicity of Li-TFSI leads to moisture uptake, which accelerates perovskite degradation and adversely affects device performance. Therefore, constructing a perovskite/spiro-OMeTAD interface with improved stability is essential yet challenging. Herein, the perovskite/spiro-OMeTAD interface was modified using two dipole molecules that promoted effective band alignment at the interface. Furthermore, introducing oxygen dipole (O-Dipoles) molecules effectively suppressed trap states, resulting in efficient hole extraction at the perovskite/HTL interface. Consequently, the O-Dipoles-modified device was more efficient and stable than the control. This study emphasizes the importance of interfacial molecular design in simultaneously maximizing the efficiency and long-term stability of PSCs.