title: Formation and evolution of the unexpected PbI2 phase at the interface during the growth of evaporated perovskite films.
abstract: The interface chemistry and evolution of the evaporated perovskite films on ITO, pedot/ITO, Si and glass substrates are studied. As evidenced by X-ray diffraction and X-ray photoemission spectroscopy (XPS) results, the PbI2 phase is found to be inevitably formed at the very initial growth stage, even under the conditions of a MAI-rich environment. The extremely low binding energy of adsorbed MAI particles on all the above substrates, as compared to that of PbI2 particles, is responsible for the presence of the PbI2 phase at the interface. The formation of both hole and electron barriers at the interface of PbI2/MAPbI3, as evidenced by XPS measurements, could block carrier transport into the electrode and thus deteriorate solar cell performance. This result reveals the origin of the poor performance of perovskite solar cells (PSCs) by the vacuum evaporation method, and may help to improve the performance of PSCs made using the vacuum evaporation method.
authors.affiliation: School of Materials Science and Engineering, Shanghai University, 99 Shangda Road, Shanghai 200444, China. ljwang@shu.edu.cn runxu@staff.shu.edu.cn.
authors.forename: Haitao
authors.initials: H
authors.lastname: Xu
authors.forename: Yanglin
authors.initials: Y
authors.lastname: Wu
authors.forename: Jian
authors.initials: J
authors.lastname: Cui
authors.forename: Chaowei
authors.initials: C
authors.lastname: Ni
authors.forename: Fuzong
authors.initials: F
authors.lastname: Xu
authors.forename: Jiang
authors.initials: J
authors.lastname: Cai
authors.forename: Feng
authors.initials: F
authors.lastname: Hong
authors.forename: Zebo
authors.initials: Z
authors.lastname: Fang
authors.forename: Wenzhen
authors.initials: W
authors.lastname: Wang
authors.forename: Jiabin
authors.initials: J
authors.lastname: Zhu
authors.forename: Linjun
authors.initials: L
authors.lastname: Wang
authors.forename: Run
authors.initials: R
authors.lastname: Xu
authors.forename: Fei
authors.initials: F
authors.lastname: Xu