Optoelectronic and stability properties of quasi-2D alkylammonium based perovskites

TL;DR

This study combines theoretical DFT calculations and experimental validation to analyze the electronic, optical, and stability properties of quasi-2D alkylammonium perovskites, revealing trends related to halogen type and cation size.

Contribution

It provides new insights into the stability and electronic properties of quasi-2D perovskites, supported by both computational and experimental data.

Findings

Halogen ions influence band structure, stability, and defect formation.

Experimental validation confirms theoretical predictions on stability and optical properties.

Bromide and chloride-based compounds show enhanced stability.

Abstract

Electronic and stability properties of quasi-2D alkylammonium perovskites are investigated using density functional theory (DFT) calculations and validated experimentally on selected classes of compounds. Our analysis is focused on perovskite structures of formula (A)$_2$(A$'$)$_{n-1}$Pb$_n$X$_{3n+1}$, with large cations A = butyl-, pentyl-, hexylammonium (BA, PA, HXA), small cations A$'$ = methylammonium, formamidinium, ethylammonium, guanidinium (MA,FA,EA,GA) and halogens X = I, Br, Cl. The role of the halogen ions is outlined for the band structure, stability and defect formation energies. Two opposing trends are found for the absorption efficiency versus stability, the latter being assessed with respect to possible degradation mechanisms. Experimental validation is performed on quasi-2D perovskites based on pentylammonium cations, namely: (PA)$_2$PbX$_4$ and (PA)$_2$(MA)Pb$_2$X$_7$, synthesized by antisolvent-assisted vapor crystallization. Structural and optical analysis are inline with the DFT based calculations. In addition, the thermogravimetric analysis shows an enhanced stability of bromide and chloride based compounds, in agreement with the theoretical predictions.