Electronic Structure of AgBi2I7 Perovskite: Substitution Effects and Structural Stability

Axel Erbing^a, Hua Wu^b^,^d, Huimin Zhu^b, Malin B. Johansson^b, Gabriel J. Man^c, Soham Mukherjee^c, Håkan Rensmo^c, Erik M. J. Johansson^b, Michael Odelius^a

^aDepartment of Physics, Albanova University Center, Stockholm University, Stockholm, Sweden

^bUppsala University, Ångström Laboratory, Sweden, Lägerhyddsvägen, 1, Uppsala, Sweden

^cDepartment of Physics and Astronomy; Molecular and Condensed Matter Physics, Uppsala University, Box 516, Uppsala, Sweden

^dState Key Laboratory on Integrated Optoelectronics and College of Electronic Science and Engineering, Jilin University, Changchun, China

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)

Roma, Italy, 2020 May 12th - 14th

Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo

Poster, Axel Erbing, 257
Publication date: 6th February 2020

During the last decade, perovskite-based solar cells have become a topic of intense research in the field of photovoltaics, with the hope of developing a material for economically viable use. The current most popular perovskite photovoltaics rely on organic-inorganic lead-based materials [1, 2], which pose environmental and health hazards due to the toxicity of lead. To significantly reduce this risk, the substitution of lead with other metals, such as the much less toxic bismuth, have been attempted [3].

The electronic structure of perovskite materials can be modeled using periodic density functional theory (DFT). The Kohn-Sham orbitals are used to interpret the photoelectron spectra and the orbital energies are associated with the electron binding energies. Hence, it is possible to extract both the band structure and the projected density of states (PDOS) from the calculations which are important to understand a materials photovoltaic properties.

In this work, cubic phase AgBi2I7 is studied theoretically with DFT. In particular, the effects on the electronic structure due to gradual antimony and bromine substitutions in the crystal are investigated, with the aim of understanding how these changes affect the cell efficiency. The structural stability of the system and how it relates to the relative distribution of Ag and vacancies is also studied. Using Monte Carlo sampling, trends in the total energy of the system as a function of the atom distribution within crystal sites are examined to understand why certain configurations are more stable under geometry optimization than others. The theoretical work is carried out in close collaboration experiments and is supported by X-ray photoelectron spectroscopy, UV-Vis spectra, and X-ray diffraction measurements.

References:

[1] Kojima, A.; Teshima, K.; Shirai, Y.; Miyasaka, T. Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells. J. Am. Chem. Soc. 2009, 131, 6050−6051.

[2] Lindblad, R.; Jena, N. K.; Philippe, B.; Oscarsson, J.; Bi, D.; Lindblad, A.; Mandal, S.; Pal, B.; Sarma, D. D.; Karis, O. Electronic Structure of CH3NH3PbX3 Perovskites: Dependence on the Halide Moiety. J. Phys. Chem. C. 2015, 119, 1818–1825

[3] Zhu, H.; Pan, M.; Johansson, M. B.; Johansson, E. M. J. High Photon‐to‐Current Conversion in Solar Cells Based on Light‐Absorbing Silver Bismuth Iodide. Chem. Sus. Chem. Com. 2017, 10, 2592-2596

Acknowledgements:

This work was supported by the Swedish Energy Agency (STEM 2017-006797),
and the Swedish Research Council (2015-03956 and 2016-04590).

The theoretical modeling was made possible through generous allocations of computer time provided by the Swedish National Infrastructure for Computing (SNIC)
at the Swedish National Supercomputer Center (NSC) and the High Performance Computer Center North (HPC2N) and
Chalmers Centre for Computational Science and Engineering (C3SE), Sweden.

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