Ultrafast ion migration in hybrid perovskite polycrystalline thin films under light and suppression in single crystals

Jie Xing; Qi Wang; Qingfeng Dong; Yongbo Yuan; Yanjun Fang; Jinsong Huang

doi:10.1039/c6cp06496e

Ultrafast ion migration in hybrid perovskite polycrystalline thin films under light and suppression in single crystals

Phys Chem Chem Phys. 2016 Nov 9;18(44):30484-30490. doi: 10.1039/c6cp06496e.

Authors

Jie Xing¹, Qi Wang², Qingfeng Dong², Yongbo Yuan³, Yanjun Fang², Jinsong Huang²

Affiliations

¹ Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, 68588, NE, USA. jhuang2@unl.edu and School of Science, China University of Geosciences, Beijing, 100083, P. R. China.
² Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, 68588, NE, USA. jhuang2@unl.edu.
³ Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, 68588, NE, USA. jhuang2@unl.edu and Hunan Key Laboratory of Super Microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha, Hunan 410083, P. R. China.

PMID: 27782266
DOI: 10.1039/c6cp06496e

Abstract

Understanding the influence of light on ion migration in organic-inorganic halide perovskite (OIHP) materials is important to understand the photostability of perovskite solar cells. We reveal that light could greatly reduce the ion migration energy barrier in both polycrystalline and single crystalline OIHP. The activation energies derived from conductivity measurement under 0.25 Sun decrease to less than one half of the values in the dark. A typical ion drift velocity in CH₃NH₃PbI₃ polycrystalline films is 1.2 μm s^-1 under 1 Sun, compared with 0.016 μm s^-1 under 0.02 Sun. Ion migration across the photoactive layers in most OIHP devices thus takes only subseconds under 1 Sun illumination, which is much shorter than what it was thought to take. Most important of all, ion migration through a single crystal surface is still too slow to be observed even after illumination for two days due to the large ion diffusion activation energy, >0.38 eV.