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Synthesis, optoelectronic properties, and charge carrier dynamics of colloidal quasi-two-dimensional Cs3Bi2I9 perovskite nanosheets

Sushant Ghimire Orcid Logo, Chris Rehhagen Orcid Logo, Saskia Fiedler, Urvi Parekh, Rostyslav Lesyuk, Stefan Lochbrunner Orcid Logo, Christian Klinke Orcid Logo

Nanoscale, Volume: 15, Issue: 5, Pages: 2096 - 2105

Swansea University Author: Christian Klinke Orcid Logo

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DOI (Published version): 10.1039/d2nr06048e

Abstract

Non-toxicity and stability make two-dimensional (2D) bismuth halide perovskites better alternatives to lead-based ones for optoelectronic applications and catalysis. In this work, we synthesize sub-micron size colloidal quasi-2D Cs3Bi2I9 perovskite nanosheets and study their generation and relaxatio...

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Published in: Nanoscale
ISSN: 2040-3364 2040-3372
Published: Royal Society of Chemistry (RSC) 2022
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URI: https://cronfa.swan.ac.uk/Record/cronfa62450
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Abstract: Non-toxicity and stability make two-dimensional (2D) bismuth halide perovskites better alternatives to lead-based ones for optoelectronic applications and catalysis. In this work, we synthesize sub-micron size colloidal quasi-2D Cs3Bi2I9 perovskite nanosheets and study their generation and relaxation of charge carriers. Steady-state absorption spectroscopy reveals an indirect bandgap of 2.07 eV, which is supported by the band structure calculated using density functional theory. The nanosheets show no detectable photoluminescence at room temperature at near bandgap excitation which is attributed to the indirect bandgap. However, cathodoluminescence spanning a broad range from 500 nm to 750 nm with an asymmetric and Stokes-shifted emission is observed, indicating the phonon- and trap-assisted recombination of charge carriers. We study the ultrafast charge carrier dynamics in Cs3Bi2I9 nanosheets using femtosecond transient absorption spectroscopy. The samples are excited with photon energies higher than their bandgap, and the results are interpreted in terms of hot carrier generation (<1 ps), thermalization with local phonons (∼1 ps), and cooling (>30 ps). Further, a relatively slow relaxation of excitons (≳3 ns) at the band edge suggests the formation of stable polarons which decay nonradiatively by releasing phonons.
College: Faculty of Science and Engineering
Funders: S. G. acknowledges Alexander von Humboldt-Stiftung/ Foundation for the postdoctoral research fellowship. C. K. acknowledges the European Regional Development Fund of the European Union for funding the PL spectrometer (GHS-20- 0035/P000376218) and X-ray diffractometer (GHS-20-0036/ P000379642) and the Deutsche Forschungsgemeinschaft (DFG) for funding an electron microscope ThermoFisher Talos L120C (INST 264/188-1 FUGG) and for supporting the collaborative research center SFB 1477 “Light-Matter Interactions at Interfaces (LiMatI)”, project number 441234705. C. R. acknowledges the financial support by the DFG via the priority program SPP 2102 (LO 714/11-1) and the Friedrich-Naumann Foundation for the graduate scholarship.
Issue: 5
Start Page: 2096
End Page: 2105

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