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Degradation by Exposure of Coevaporated CH3NH3PbI3 Thin Films

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posted on 2015-10-22, 00:00 authored by Youzhen Li, Xuemei Xu, Chenggong Wang, Congcong Wang, Fangyan Xie, Junliang Yang, Yongli Gao
Degradation of coevaporated CH3NH3PbI3 thin films were investigated with X-ray photoelectron spectroscopy and X-ray diffraction as the films were subjected to exposure of oxygen, low pressure atmospheric air, atmospheric air, or H2O. The coevaporated thin films have consistent stoichiometry and crystallinity suitable for detailed surface analysis. The results indicate that CH3NH3PbI3 is not sensitive to oxygen. Even after 1013 Langmuir (L, one L equals 10–6 Torr s) oxygen exposure, no O atoms could be found on the surface. The film is not sensitive to dry air as well. A reaction threshold of about 2 × 1010 L is found for H2O exposure, below which no CH3NH3PbI3 degradation takes place, and the H2O acts as an n-dopant. Above the threshold, the film begins to decompose, and the amount of N and I decrease quickly, leaving the surface with PbI2, hydrocarbon complex, and O contamination.

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