Highly Improved Efficiency and Stability of 2D Perovskite Solar Cells via Bifunctional Inorganic Salt KPF6 Modified NiO x Hole Transport Layer

In general, improving the electrical conductivity of bare NiO x film and alleviating the undesired energy level mismatch by interface engineering are operative to enhance the property of 2D perovskite solar cells (2D PSCs) based on NiO x . Herein, the NiO x /2D perovskite interface is modified by inorganic salt KPF 6 to improve the interfacial contact and conductivity of NiO x . It is revealed that KPF 6 not only improves the conductivity of NiO x through the formation of Ni  F coordination bond with NiO x by PF 6 - but also promotes the energy level matching between NiO x and the 2D perovskite layer. Thus, KPF 6 -modified NiO x greatly enhances the extraction ability of hole carriers in 2D perovskite layers and improves the crystallinity of 2D perovskite films. Accordingly, the NiO x /KPF 6 -based 2D PSCs attain an optimal power conversion efficiency (PCE) of 14.34%. Meanwhile, the KPF 6 modified device without sealed maintains 93% of its original PCE for 600 h on a 60 °C hot plate filled with nitrogen and 72% after aging for 600 h with a humidity of 35 ± 10% in the atmosphere, respectively. This study demonstrates the effectiveness of using inorganic salts to modify NiO x hole transport layers to augment the optoelectronic properties and stability of 2D PSCs.