Electronic structure evolution of fullerene on CH₃NH₃PbI₃

Authors

Chenggong Wang, University of Rochester
Congcong Wang, University of Rochester
Xiaoliang Liu, Central South University
John Kauppi, University of Rochester
Yuchuan Shao, University of Nebraska-Lincoln
Zhengguo Xiao, University of Nebraska-LincolnFollow
Cheng Bi, University of Nebraska-Lincoln
Jinsong Huang, University of Nebraska-LincolnFollow
Yongli Gao, University of Rochester

Document Type

Article

Date of this Version

2015

Citation

APPLIED PHYSICS LETTERS 106, 111603 (2015)

Comments

Copyright 2015 AIP Publishing LLC.

Abstract

The thickness dependence of fullerene on CH₃NH₃PbI₃ perovskite film surface has been investigated by using ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy (XPS), and inverse photoemission spectroscopy (IPES). The lowest unoccupied molecular orbital and highest occupied molecular orbital (HOMO) can be observed directly with IPES and UPS. It is observed that the HOMO level in fullerene shifts to lower binding energy. The XPS results show a strong initial shift of core levels to lower binding energy in the perovskite, which indicates that electrons transfer from the perovskite film to fullerene molecules. Further deposition of fullerene forms C₆₀ solid, accompanied by the reduction of the electron transfer. The strongest electron transfer happened at 1/4 monolayer of fullerene.