Insights into the electron transport performance of the FAPbI3/SnO2 interface

The interface engineering between the photovoltaic layer and the electron transport layer (ETL) is critical to achieve high-efficiency perovskite solar cells (PSCs). Herein, the FAPbI(3)/SnO2 interface properties are studied using first-principles calculations. The FAPbI(3)/SnO2 interface has six types of contact (PbI2/O, PbI2/SnO, PbI2/Sn, FAI/O, FAI/SnO and FAI/Sn), which have good dynamic stability at room temperature (300 K) by canonical ab initio molecular dynamics simulations. The interfacial properties are completely different for the diverse interface contact types. The PbI2/SnO interface contact has the best electron transport performance by analyzing the interface coupling, interface charge transfer and interface electronic structure. The O dangling bonds on the SnO2 surface can reconstruct the FAPbI(3) surface and impair the interfacial properties due to the large electronegativity of the O atoms. Interface modification using alkali metal elements (Li, Na, K, Rb and Cs), especially potassium and rubidium, can effectively passivate the O dangling bonds and improve interface properties. In addition, the interfacial properties after modification can be further improved by applying compressive strain. Our results reveal the novel FAPbI(3)/SnO2 interfacial properties and provide a new theoretical approach to effectively improve the performance of PSCs through interface engineering.