Impact of n-Butylammonium Bromide on the Chemical and Electronic Structure of Double-Cation Perovskite Thin Films

Dirk Hauschild; Linsey Seitz; Saba Gharibzadeh; Ralph Steininger; Nan Jiang; Wanli Yang; Ulrich Wilhelm Paetzold; Clemens Heske; Lothar Weinhardt

doi:10.1021/acsami.1c15707

Impact of n-Butylammonium Bromide on the Chemical and Electronic Structure of Double-Cation Perovskite Thin Films

ACS Appl Mater Interfaces. 2021 Nov 10;13(44):53202-53210. doi: 10.1021/acsami.1c15707. Epub 2021 Oct 28.

Authors

Dirk Hauschild^{1

2

3}, Linsey Seitz¹, Saba Gharibzadeh^{4

5}, Ralph Steininger¹, Nan Jiang³, Wanli Yang⁶, Ulrich Wilhelm Paetzold^{4

5}, Clemens Heske^{1

2

3}, Lothar Weinhardt^{1

2

3}

Affiliations

¹ Institute for Photon Science and Synchrotron Radiation (IPS), Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen 76344, Germany.
² Institute for Chemical Technology and Polymer Chemistry (ITCP), Karlsruhe Institute of Technology (KIT), Karlsruhe 76131, Germany.
³ Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154, United States.
⁴ Institute of Microstructure Technology (IMT), Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen 76344, Germany.
⁵ Light Technology Institute (LTI), Karlsruhe Institute of Technology (KIT), Karlsruhe 76131, Germany.
⁶ Advanced Light Source (ALS), Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.

PMID: 34709800
DOI: 10.1021/acsami.1c15707

Abstract

2D/3D perovskite heterostructures have emerged as a promising material composition to reduce nonradiative recombination in perovskite-based LEDs and solar cells. Such heterostructures can be created by a surface treatment with large organic cations, for example, n-butylammonium bromide (BABr). To understand the impact of the BABr surface treatment on the double-cation (Cs_0.17FA_0.83Pb(I_0.6Br_0.4)₃) (FA = formamidinium) perovskite thin film and further optimize the corresponding structures, an in-depth understanding of the chemical and electronic properties of the involved surfaces, interfaces, and bulk is required. Hence, we study the impact of the BABr treatment with a combination of surface-sensitive X-ray photoelectron spectroscopy and bulk-sensitive resonant inelastic soft X-ray scattering (RIXS). A quantitative analysis of the BABr-treated perovskite thin film shows a modified chemical perovskite surface environment of carbon, nitrogen, bromine, iodine, and lead, indicating that the treatment leads to a perovskite surface with a modified composition and bonding structure. With K-edge RIXS, the local environment at the nitrogen and carbon atoms is probed, allowing us to identify the presence of BABr in the perovskite bulk albeit with a modified bonding environment. This, in turn, identifies a "hidden parameter" for the optimization of the BABr treatment and overall performance of 2D/3D perovskite solar cell absorbers.

Keywords: 2D/3D perovskite heterostructure; X-ray absorption spectroscopy; X-ray emission spectroscopy; n-butylammonium bromide surface treatment; perovskite-based solar cells; photoelectron spectroscopy; resonant inelastic soft X-ray scattering.