Cadmium Doping: Incorporation and Phase Segregation in Mixed-Cation and Mixed-Halide Lead Perovskites from Solid-State NMR
Dominik Kubicki a, Daniel Prochowicz a b, Albert Hofstetter a, Shaik Zakeeruddin a, Michael Grätzel a, Lyndon Emsley a
a Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
b Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Oral, Dominik Kubicki, presentation 154
Publication date: 11th February 2019

Cadmium doping has recently emerged as a strategy for supressing atomic vacancies and improving stability of perovskite solar cells (PSCs), as well as a means of postsynthetic tailoring of perovskite nanocrystals.[1-3] While the beneficial effects of cadmium doping are evident, the atomic-level microstructure of cadmium inside the doped perovskites remains unclear. We have recently shown that solid-state NMR is perfectly suited for probing dopant incorporation and phase heterogeneity in complex perovskite materials since it directly reveals the local atomic environment of the dopant.[4-6]

Here, using 113Cd MAS NMR at 21.1 T we provide for the first time atomic-level characterization of the cadmium-containing phases that are formed upon cadmium doping of multi-cation and multi-anion lead-halide perovskites. Contrary to current belief, cadmium is not incorporated into organic-inorganic lead halide perovskites and forms secondary non-perovskite phases instead. We also find that, consistent with current understanding, cadmium is incorporated into the all-inorganic CsPbBr3 perovskite.

Figure: Schematic representation of the previously suggested scenario for cadmium incorporation into the perovskite lattice: (a) parent APbI3 lattice (A=MA, FA, Cs+), (b) B-site replacement.

This work was supported by Swiss National Science Foundation Grant No. 200021_160112. D. P. acknowledges financial support from the HOMING programme of the Foundation for Polish Science co-financed by the European Union under the European Regional Development Fund (POIR.04.04.00-00-5EE7/18-00). S. Z. and M. G acknowledge funding from the EU Horizon 2020 programme, through the FET Open Research and Innovation Action, grant agreement no. 687008. M. G. and and S. Z thank the King Abdulaziz City for Science and Technology (KACST) and the SNSF for a joint research project (IZLRZ2_164061) under Scientific & Technological Cooperation Programme Switzerland-Russia.

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