Ion-Dipole Interaction for Self-Assembled Monolayers: A New Strategy for Buried Interface in Inverted Perovskite Solar Cells

Nickel oxide (NiOX) has a crucial role in enhancing the efficiency and stability of p-i-n inverted perovskite solar cells (PSCs), which hold great potential for commercialization. However, improving contact passivation between perovskites and NiOX is a challenge due to a hindered buried interface. In order to address this issue, self-assembled monolayers (SAMs) are introduced as a buffer layer to prevent direct contact and non-radiative recombination. While, the large dipole moment of SAMs increases the work function of NiOX, which is crucial for enhancing hole transport performance, given the low interfacial potential barrier for hole transfer. By a combination of the first-principles calculations, drive-level capacitance profiling, and transient absorption spectrum characterization, the understanding of the ion-dipole interactions and interface passivation mechanism of potassium fluoride (KF) ultra-thin buffer layer between SAMs and perovskites is provided. The efficiency of inverted PSCs as high as 23.25% is obtained, and the unencapsulated devices kept 90% of initial efficiency following 1400 h aging under nitrogen, which demonstrate remarkable long-term stability as well. This novel strategy highlights the significance of SAMs dipole moment at the NiOX/perovskites interface and provides a new approach to address buried interfaces for high-efficiency and long-term stability in inverted PSCs. A new hybrid interface layer, based on an ionic and self-assembled monolayer, strengthens a unidirectional net dipole moment between the hole transport layer and perovskite through ion-dipole interactions between fluorine and 2PACz, which further enhances the charge extraction and reduces the non-radiative recombination rates. In addition, stability is improved owing to the holistic interface passivation of the buried NiOX/perovskite interface. image