How Can Halide Perovskites Have such Low Defect Densities?
David Cahen a b
a Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100, Israel.
b 1Department of Chemistry, Center for Nanotechnology & Advanced Materials, Bar Ilan University, Ramat-Gan, Ramat-Gan, 52900, Israel
nanoGe Perovskite Conferences
Proceedings of nanoGe International Conference on Perovskite Solar Cells, Photonics and Optoelectronics (NIPHO19)
International Conference on Perovskite Thin Film Photovoltaics
Jerusalem, Israel, 2019 February 24th - 27th
Organizers: Lioz Etgar and Kai Zhu
Invited Speaker, David Cahen, presentation 013
Publication date: 21st November 2018

The low defect density in halide perovskites (HaPs) is a welcome present for most device applications, one that has certainly increased the popularity of these materials. Still, we should pause a minute and ask what are the fundamental reasons that allow a material that can be made in “quick and dirty” (albeit not always reproducible) fashion at low temperatures (around RT), at times in ambient, as films or single crystals to have such low defect density (down to 1014 cm-3 for solution-grown and 1013 cm-3 for vacuum-deposited films and 1010 cm-3 or less for single crystals). I note that these defect densities are all deduced from the common measurements for charged or neutral imperfections, which are indirect ones. Still also more direct, qualitative measurements, such as surface photovoltage, differential external quantum efficiency, scanning tunneling and photothermal deflection spectroscopies, all indicate GaAs-like or lower defect densities.

I hope to show in 3.5 months from writing these lines that this behaviour reflects a fundamental property of these materials, with a rather simple basis. The talk will combine experimental results from several sources, including our own, for thermodynamic, optical, and electrical data. It is plausible that our conclusions can be generalized to help look for other ultra-low defect density materials.

The work is done with Igor Lubomirsky, Yevgeny Rakita (part of his PhD thesis) and Gary Hodes.

I thank David Egger (Regensburg), Omer Yaffe, Leeor Kronik (Weizmann Inst.) and others for ongoing discussions.

Support,from the Minerva Centre for Self-Repairing Systems for Energy & Sustainability at the Weizmann Institute, is gratefully acknowledged.

© Fundació Scito
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