Photo de-mixing in Dion-Jacobson two-dimensional mixed halide perovskites

TL;DR

This study reveals that Dion-Jacobson 2D mixed halide perovskites undergo reversible photo de-mixing and structural changes under illumination, impacting their optoelectronic properties and thermodynamic stability.

Contribution

It demonstrates the photo-induced de-mixing process in 2D hybrid perovskites and explores its reversibility and thermodynamic implications.

Findings

Photo de-mixing occurs under illumination

De-mixed phases are reversible in the dark

Light induces irreversible structural changes

Abstract

Two-dimensional (2D) halide perovskites feature a versatile structure, which not only enables the fine-tuning of their optoelectronic properties but also makes them appealing as model systems to investigate the fundamental properties of hybrid perovskites. In this study, we analyzed the changes in the optical absorption of 2D Dion-Jacobson mixed halide perovskite thin films (encapsulated) based on (PDMA)Pb(I0.5Br0.5)4 (PDMA: 1,4-phenylenedimethanammonium spacer) exposed to a constant illumination. We demonstrate that these 2D mixed-halide perovskites undergo photo de-mixing with direct transformation from the pristine phase to the de-mixed phases. Almost complete re-mixing of these phases occurs when the sample is left in the dark, showing that the process is reversible in terms of optical properties. On the other hand, exposure to light appears to induce structural changes in the thin film that are not reversible in the dark. We have further investigated temperature-dependent absorption measurements under light to extract the photo de-mixed compositions and to map the photo-miscibility-gap. This work thereby reveals that photo de-mixing occurs in Dion-Jacobson two-dimensional hybrid perovskites and provides strategies to address the role of light in the thermodynamic properties of these materials.