The Atomic-level Structure of Bandgap Engineered Double Perovskite Alloys Cs2AgIn1−xFexCl6
Fuxiang Ji a, Feng Wang a, Libor Kobera a, Sabina Abbrent b, Jiri Brus b, Weihua Ning b, Feng Gao a
a Department of Physics, Chemistry and Biology Linkoping University 58183, Linkoping, Sweden
b Institute of Macromolecular Chemistry of the Czech Academy of Sciences, Heyrovskeho nam. 2, 162 06, Prague 6, Czech Republic.
Proceedings of 13th Conference on Hybrid and Organic Photovoltaics (HOPV21)
Online, Spain, 2021 May 24th - 28th
Organizers: Marina Freitag, Feng Gao and Sam Stranks
Poster, Fuxiang Ji, 180
Publication date: 11th May 2021

Although lead-free halide double perovskites are considered as promising alternatives to lead halide perovskites for optoelectronic applications, state-of-the-art double perovskites are limited by their large bandgap. The doping/alloying strategy, key to bandgap engineering in traditional semiconductors, has also been employed to tune the bandgap of halide double perovskites. However, this strategy has yet to generate new double perovskites with suitable bandgaps for practical applications, partially due to the lack of fundamental understanding of how the doping/alloying affects the atomic-level structure. Here, we take the benchmark double perovskite Cs2AgInCl6 as an example to reveal the atomic-level structure of double perovskite alloys (DPAs) Cs2AgIn1−xFexCl6 (x = 0–1) by employing solid-state nuclear magnetic resonance (ssNMR). The presence of paramagnetic alloying ions (e.g. Fe3+ in this case) in double perovskites makes it possible to investigate the nuclear relaxation times, providing a straightforward approach to understand the distribution of paramagnetic alloying ions. Our results indicate that paramagnetic Fe3+ replaces diamagnetic In3+ in the Cs2AgInCl6 lattice with the formation of [FeCl6]3−·[AgCl6]5− domains, which show different sizes and distribution modes in different alloying ratios. This work provides new insights into the atomic-level structure of bandgap engineered DPAs, which is of critical significance in developing efficient optoelectronic/spintronic devices.

This work was financially supported by Knut and Alice Wallenberg Foundation, the Swedish Energy Agency (2018-004357), VR Starting Grant (2019–05279), Carl Tryggers Stiftelse, Olle Engkvist Byggmästare Stiftelse, the STINT grant (CH2018-7655), the National Natural Science Foundation of China (61704078), the Grant Agency of the Czech Republic (Grant GA19-05259S), and the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU No. 2009-00971). F. G. is a Wallenberg Academy Fellow. F. J. was supported by the China Scholarship Council (CSC).

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