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Identifying and controlling phase purity in 2D hybrid perovskite thin films

Lookup NU author(s): Dr Pablo Docampo

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This is the authors' accepted manuscript of an article that has been published in its final definitive form by Royal Society of Chemistry, 2018.

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Abstract

Two-dimensional (2D) hybrid perovskites have attracted considerable attention due to their enormous structural and electronical variability, making this class of semiconductors interesting for photovoltaics, light-emitting diodes and lasers. 2D perovskites consist of sheets of bulky organic cations alternately sandwiched by layers of lead halide octahedra. The properties of these materials strongly depend on the thickness of the octahedra layers, defined by the number of octahedra sheets in a layer, n. Consequently, controlling the layer thickness purity (i.e. minimizing the spread in n) is important for any 2D perovskite thin film application. Here, we show that using rationally chosen solvent additives in the precursor solution offers a facile way to control the crystal disorder in 2D perovskites films. Our method leads to significantly reduced variation in n around the target value relative to films obtained by conventional fast-crystallization methods without solvent additives. The improved phase purity in optimized n = 2 and n = 3 films is verified by X-ray diffraction, UV-Vis absorption, and photoluminescence measurements. Additionally, we find that 2D perovskite films with n³ 2 arising from additive-assisted growth exhibit an unusual crystal orientation with the perovskite interlayers predominantly aligned parallel to the substrate, which we assign to the slow crystallization process induced by the lead-complexing solvent additives. Improved control over the phase purity translates into a better control of the optoelectronic properties of 2D perovskite films. Furthermore, the unusual horizontal crystal orientation of n = 2 and n = 3 films makes this family of tunable organic-inorganic perovskites promising for applications where lateral charge transport is desired, thus enlarging the potential for thin film-based applications of the 2D perovskites.


Publication metadata

Author(s): Hu Y, Spies LM, Alonso-Alvarez D, Mocherla P, Jones H, Hanisch J, Bein T, Barnes PRF, Docampo P

Publication type: Article

Publication status: Published

Journal: Journal of Materials Chemistry A

Year: 2018

Volume: 6

Issue: 44

Pages: 22215-22225

Print publication date: 28/11/2018

Online publication date: 31/08/2018

Acceptance date: 28/08/2018

Date deposited: 04/09/2018

ISSN (print): 2050-7488

ISSN (electronic): 2050-7496

Publisher: Royal Society of Chemistry

URL: https://doi.org/10.1039/C8TA05475D

DOI: 10.1039/C8TA05475D


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