Defect Passivation with Metal Cations toward Efficient and Stable Perovskite Solar Cells Exceeding 22.7% Efficiency

Numerous defects are present on the surface and at the grain boundaries of halide perovskite, which induce charge recombination and then impede the further enhancement of power conversion efficiency (PCE) and long-term stability of halide perovskite solar cells (PSCs). Consequently, it is highly desirable to decrease the defect density in order to improve the performance of PSCs. Here, we employ metal cations to passivate these defects by incorporating Cd2+ into the perovskite active layer. It is revealed that Cd2+ can not only adjust crystal growth but also reduce the defect density and restrain the charge recombination, which makes charge transfer more effective from perovskite layers to charge transport layers. Meanwhile, we mainly discuss the impact of the incorporated Cd2+ amount on the performance of CsFAMA perovskite films and devices. By controlling Cd2+ amount, a series of PSCs with good performance are obtained. A champion device is obtained at 0.5% Cd2+-incorporated amount with a high PCE of 21.95%. This device exhibits a good long-term stability with about 12% PCE loss after 42 days in an ambient environment with about 50% relative humidity at room temperature, while the control one loses about 17% of its initial efficiency under the same conditions. Furthermore, we improve the properties of the Cd2+-incorporated CsFAMA PSCs by using KCl to passivate the CSCO/perovskite interface, in which an optimized PCE is up to 22.75%.