Dual Passivation of Perovskite and SnO(2) for High‐Efficiency MAPbI(3) Perovskite Solar Cells

So far, most techniques for modifying perovskite solar cells (PSCs) focus on either the perovskite or electron transport layer (ETL). For the sake of comprehensively improving device performance, a dual‐functional method of simultaneously passivating trap defects in both the perovskite and ETL films is proposed that utilizes guidable transfer of Eu(3+) in SnO(2) to perovskite. Europium ions are distributed throughout the SnO(2) film during the formation process of SnO(2), and they can diffuse directionally through the SnO(2)/perovskite interface into the perovskite, while most of the europium ions remain at the interface. Under the synergistic effect of distributed Eu(3+) in the SnO(2) and aggregated Eu(3+) at the interface, the electron mobilities of ETLs are evidently improved. Meanwhile, diffused Eu(3+) ions passivate the perovskite to reduce trap densities at the grain boundaries, which can dramatically elevate the open‐circuit voltage (V (oc)) of PSCs. Finally, the mainly PSCs coated on SnO(2):Eu(3+) ETL achieve a power conversion efficiency of 20.14%. Moreover, an unsealed device degrades by only 13% after exposure to ambient atmosphere for 84 days.