Passivation Mechanism Exploiting Surface Dipoles Affords High-Performance Perovskite Solar Cells.

The employment of 2D perovskites is a promising approach to tackling the stability and voltage issues inherent in perovskite solar cells. It remains unclear, however, whether other perovskites with different dimensionalities have the same effect on efficiency and stability. Here, we report the use of quasi-3D azetidinium lead iodide (AzPbI) as a secondary layer on top of the primary 3D perovskite film that results in significant improvements in the photovoltaic parameters. Remarkably, the utilization of AzPbI leads to a new passivation mechanism due to the presence of surface dipoles resulting in a power conversion efficiency (PCE) of 22.4%. The open-circuit voltage obtained is as high as 1.18 V, which is among the highest reported to date for single junction perovskite solar cells, corresponding to a voltage deficit of 0.37 V for a band gap of 1.55 eV.