Rapid improvement of the stability of metal halide perovskite materials is required to enable their adoption for energy production at terawatt scale. To understand the role of the active layer stability in these devices we use in situ X-ray diffraction to observe the evolution in structural stability across mixed A-site APbI3 materials where the A-site is a combination of formamidinium, Cs, and/or methylammonium. During device operation we observe spatial de-mixing and phase segregation into more pure constituent phases. Using complementary first-principles calculations of mixed A-site halide perovskites, a hypothesized framework explaining the experimentally observed mixing and de-mixing in these systems is presented and then validated using in situ X-ray diffraction and spatially resolved time of flight secondary ion mass spectrometry. Taken together, these results indicate that stability is not only a function of device architecture or chemical formulation, but that the processing strategy is critically important in synthesizing the most energetically favorable state and therefore the most stable device systems. This study reconciles disparate reports within the literature and also highlights the limitations of shelf life studies to ascertain stability as well as the importance of testing devices under operational conditions.
Bibliographical noteFunding Information:
The authors wish to thank Fei Zhang for providing samples for TOF-SIMs analysis. This work was supported by the U.S. Department of Energy (DOE) Solar Energy Technology Office (SETO) of the Energy Efficiency and Renewable Energy (EERE) award for the De-risking Halide Perovskite Solar Cells project at the National Renewable Energy Laboratory under Contract No. DE-AC36-08-GO28308 managed and operated by the Alliance for Sustainable Energy, LLC. Theory portions of this research used computational resources sponsored by the DOE Office of Energy Efficiency and Renewable Energy and located at the National Renewable Energy Laboratory. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, was supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515.
J. A. C. was supported by the Department of Energy, Office of Energy Efficiency and Renewable Energy Postdoctoral Research Award under contract number DE-SC00014664. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.
© 2019 The Royal Society of Chemistry.
ASJC Scopus subject areas
- Environmental Chemistry
- Renewable Energy, Sustainability and the Environment
- Nuclear Energy and Engineering