Dedoping of Lead Halide Perovskites Incorporating Monovalent Cations.
American Chemical Society (ACS)
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Abdi-Jalebi, M., Pazoki, M., Philippe, B., Dar, M. I., Alsari, M., Sadhanala, A., Divitini, G., et al. (2018). Dedoping of Lead Halide Perovskites Incorporating Monovalent Cations.. ACS nano, 12 (7), 7301-7311. https://doi.org/10.1021/acsnano.8b03586
We report significant improvements in the optoelectronic properties of lead halide perovskites with the addition of monovalent ions with ionic radii close to Pb2+. We investigate the chemical distribution and electronic structure of solution processed CH3NH3PbI3 perovskite structures containing Na+, Cu+ and Ag+, which are lower valence metal ions than Pb2+ but have similar ionic radii. Synchrotron x-ray diffraction reveals a pronounced shift in the main perovskite peaks for the monovalent cation-based films, suggesting incorporation of these cations into the perovskite lattice, as well as a preferential crystal growth in Ag+ containing perovskite structures. Furthermore, the synchrotron X-ray photoelectron measurements show a significant change in the valence band position for Cu- and Ag-doped films although the perovskite bandgap remains the same, indicating a shift in the Fermi level position towards the middle of the bandgap. Such a shift infers that incorporation of these monovalent cations de-dope the n-type perovskite films when formed without added cations. This de-doping effect leads to cleaner bandgaps as reflected by the lower energetic disorder in the monovalent cation doped perovskite thin films as compared to pristine films. We also find that in contrast to Ag and Cu, Na locates mainly at the grain boundaries and surfaces. Our theoretical calculations confirm the observed shifts in x-ray diffraction peaks and Fermi level, as well as absence of intra-bandgap states upon energetically favorable doping of perovskite lattice by the monovalent cations. We also model a significant change in the local structure, chemical bonding of metal-halide and the electronic structure in the doped perovskites. In summary, our work highlights the local chemistry and influence of monovalent cation dopants on crystallization and the electronic structure in the doped perovskite thin films.
Is supplemented by: https://www.repository.cam.ac.uk/handle/1810/278386
Cambridge Materails Limited, Nava Technology Limited
External DOI: https://doi.org/10.1021/acsnano.8b03586
This record's URL: https://www.repository.cam.ac.uk/handle/1810/277802