Unraveling the crucial role of spacer ligands in tuning the contact properties of metal-2D perovskite interfaces

The bonding and electronic properties of electrode-2D perovskite interfaces, which play a crucial role in affecting the device performance, are investigated based on state-of-the-art density functional theory. Schottky barriers are observed at metal-PEA(2)PbI(4) interfaces with a strong Fermi level pinning effect. The interfacial Pauli-exclusion effect is found to be mainly responsible for the interfacial band realignment, irrespective of the existence of gap states. This is because of the buffer layer nature of the PEA(+) ligand which ensures negligible influence of interfacial interactions on the band edges of PEA(2)PbI(4). The Schottky barrier height can also be tuned by tailoring the quantum confinement effect in 2D perovskites. Moreover, tunable tunneling barriers and interfacial charge densities are obtainable according to different contact types. These results uncover the crucial role of the spacer ligand in modulating the contact properties of metal-2D perovskites interfaces, which is beneficial for optimizing the device performance.