Universität zu Köln

Choghaei, Maryam ORCID: 0000-0002-9428-2701, Schiffer, Maximilian, Tyagi, Viren, Righetto, Marcello ORCID: 0000-0001-5507-1445, Du, Jiaxing, Buchmüller, Maximilian, Brinkmann, Kai Oliver ORCID: 0000-0002-2124-3904, Brocks, Geert, Görrn, Patrick, Herz, Laura M. ORCID: 0000-0001-9621-334X, Tao, Shuxia ORCID: 0000-0002-3658-8497, Riedl, Thomas ORCID: 0000-0003-1084-316X and Olthof, Selina ORCID: 0000-0002-8871-1549 (2025). Odd-even effects in lead-iodide-based Ruddlesden–Popper 2D perovskites. Journal of Materials Chemistry A, 13 (24). pp. 18935-18947. Royal Society of Chemistry. ISSN 2050-7488

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Abstract

Two-dimensional (2D) halide perovskites are a versatile material class, exhibiting a layered crystal structure, consisting of inorganic metal–halide sheets separated by organic spacer cations. Unlike their 3D counterparts, 2D perovskites have less strict geometric requirements, allowing for a wider range of molecules to be incorporated. This potentially offers a way to engineer the properties of a 2D perovskite through adequate selection of the organic spacer cations. Our study systematically analyzes the effect of spacer cation length on the electronic and optical properties of Ruddlesden–Popper lead-iodide-based 2D perovskites, using alkylammonium cations of varying chain lengths. Intriguingly, no linear correlation between interlayer distance and the optical gap or valence band position is observed in our measurements. Rather it matters whether the spacer cation contains an odd or even number of carbon atoms in the chain. Notably, these odd-even effects manifest in variations of ionization energy, optical gap as well as charge carrier mobility. Density functional theory calculations reproduce the changes in optical properties, allowing us to identify the underlying mechanism: while even-numbered carbon chains pack efficiently within the organic spacer layer, the shorter odd-numbered chains increase distortions. These distortions lead to variations in the Pb–I–Pb bond angle within the inorganic sheets, resulting in the observed odd-even effect in the (opto-)electronic properties. This understanding will be helpful to make more informed choices regarding the incorporated spacer molecules which can potentially help to enhance performance when integrating such 2D perovskite interlayers into devices.

Item Type:	Article
Creators:	Creators Email ORCID ORCID Put Code Choghaei, Maryam UNSPECIFIED https://orcid.org/0000-0002-9428-2701 UNSPECIFIED Schiffer, Maximilian UNSPECIFIED UNSPECIFIED UNSPECIFIED Tyagi, Viren UNSPECIFIED UNSPECIFIED UNSPECIFIED Righetto, Marcello UNSPECIFIED https://orcid.org/0000-0001-5507-1445 UNSPECIFIED Du, Jiaxing UNSPECIFIED UNSPECIFIED UNSPECIFIED Buchmüller, Maximilian UNSPECIFIED UNSPECIFIED UNSPECIFIED Brinkmann, Kai Oliver UNSPECIFIED https://orcid.org/0000-0002-2124-3904 UNSPECIFIED Brocks, Geert UNSPECIFIED UNSPECIFIED UNSPECIFIED Görrn, Patrick UNSPECIFIED UNSPECIFIED UNSPECIFIED Herz, Laura M. UNSPECIFIED https://orcid.org/0000-0001-9621-334X UNSPECIFIED Tao, Shuxia UNSPECIFIED https://orcid.org/0000-0002-3658-8497 UNSPECIFIED Riedl, Thomas UNSPECIFIED https://orcid.org/0000-0003-1084-316X UNSPECIFIED Olthof, Selina UNSPECIFIED https://orcid.org/0000-0002-8871-1549 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-812110
Identification Number:	10.1039/D5TA01234A
Journal or Publication Title:	Journal of Materials Chemistry A
Volume:	13
Number:	24
Page Range:	pp. 18935-18947
Number of Pages:	13
Date:	19 May 2025
Publisher:	Royal Society of Chemistry
ISSN:	2050-7488
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Physical Chemistry
Subjects:	Chemistry and allied sciences
['eprint_fieldname_oa_funders' not defined]:	Publikationsfonds UzK
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/81211