Oxygen- and Water-Induced Energetics Degradation in Organometal Halide Perovskites

Organometal halide perovskites are under rapid development, and significant focus has been placed on their stability that currently presents a major obstacle for practical application. Energetics plays a vital role in charge injection/extraction and transport properties in devices. Here, we in situ investigate oxygen and water-induced energetics degradation in organometal halide perovskite films. Oxygen gas induces an upward shift of the vacuum level of the perovskite films because of the formation of an oxygen induced surface dipole, water vapor causes a significant vacuum-level downshift, and the valence band binding energy referenced to the Fermi level simultaneously increases so as to keep the ionization potential of the perovskite films unchanged. Moreover, the chemical compositions, crystalline structures, surface morphologies, and dynamical properties also are monitored and analyzed in detail. These results are indispensable to understand the degradation mechanisms and to perform the optimizations of stable materials and devices in the future.Funding Agencies|National Science Foundation of China [11604099]; Fundamental Research Funds for the Central Universities; Swedish Research Council [2016-05498]; Goran Gustafsson Foundation for Research in Nature Sciences and Medicine; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]; China Scholarship Council; Open Project of Jiangsu Key Laboratory for Carbon Based Functional Materials Devices