Self‐Formation of SnCl<sub>2</sub> Passivation Layer on SnO<sub>2</sub> Electron‐Transport Layer in Chloride–Iodide‐Based Perovskite Solar Cell
Ashraful Hossain Howlader, Shahriyar Safat Dipta, Walia Binte Tarique, Yulun Qi, Ayush Pratik, Yin Yao, Md. Anower Hossain, Ashraf Uddin
Abstract
The phenomenon of the self‐formation of a passivation layer at the interface of the perovskite/electron‐transport layer (ETL) is observed. FA 0.6 MA 0.4 PbI 3− x Cl x perovskite thin film is deposited on a SnO 2 nanoparticle thin‐film ETL. It is observed from the depth‐resolved spectroscopy that the Sn 2+ ion migrates toward the perovskite layer within the ETL. At the same time, Cl − ion also migrates toward ETL within the perovskite layer. This unique ion migration phenomenon leads us to conclude that a passivating SnCl 2 layer is formed at the perovskite/ETL interface. It is found that this SnCl 2 layer at the interface works as a passivation layer like Al 2 O 3 . There is a significant effect of this self‐formed passivating layer behind the improvement of the device's efficiency and stability. It is believed that this SnCl 2 passivation layer helps to reduce the recombination loss at the interface and boosts the performance of the perovskite solar cell (PSC). The perovskite/hole‐transport layer is also passivated with octylammonium bromide. Finally, the PSC offers a photoconversion efficiency (PCE) of 20.81% under 1 sun and AM1.5 G condition. Again, it maintains more than 80% of PCE under open‐air room conditions, white light emitting diode, and 85 °C continuous heating for more than 12 h without encapsulation.