| AVS 63rd International Symposium & Exhibition | |
| Thin Film | Friday Sessions |
| Session TF-FrM |
| Session: | CVD, ALD and Film Characterization |
| Presenter: | Xerxes Steirer, National Renewable Energy Laboratory |
| Authors: | K.X. Steirer, National Renewable Energy Laboratory P. Schulz, National Renewable Energy Laboratory G. Teeter, National Renewable Energy Laboratory V. Stevanovic, National Renewable Energy Laboratory M. Yang, National Renewable Energy Laboratory K. Zhu, National Renewable Energy Laboratory J.J. Berry, National Renewable Energy Laboratory |
| Correspondent: | Click to Email |
X-ray photoelectron spectroscopy (XPS) is used to track dynamic chemical and electronic changes in hybrid perovskite (CH3NH3PbI3) thin-films used in photovoltaic applications. We report in detail X-ray induced transformations with implications on theoretical predictions of hybrid perovskite defect tolerance. Large changes in perovskite composition are analyzed with simultaneously acquired valence band spectra. A clear and reproducible trend is found that provides evidence for vacancy-type defect formation upon X-ray irradiation as CH3NH3PbI3 is continuously converting to PbI2. Remarkably, the position of the valence band edge with respect to the Fermi level (EF) is invariant to significant losses of both CH3NH3 and I. It is not until the I/Pb ratio drops below 2.5 that EF shifts toward the valence band edge indicating that the CH3NH3PbI3 film becomes less n-type. This shift is correlated with the formation of PbI2 as demonstrated in Pb 4f and I 3d core level spectra. Results gained from these XPS studies demonstrate that the electronic structure of the hybrid perovskite compound investigated is tolerant to defects (CH3NH3 and iodine vacancies) on the order of one defect pair per octahedron.