Phase Transitions in Low-Dimensional Layered Double Perovskites: The Role of the Organic Moieties

TL;DR

This study investigates phase transitions in layered double perovskites with organic cations, revealing how organic moieties influence structural and optical properties through temperature-dependent spectroscopy.

Contribution

It demonstrates the impact of organic cation size and structure on phase transitions and optical behavior in low-dimensional layered double perovskites.

Findings

Phase transitions detected via Raman spectroscopy in both inorganic and organic components.

Organic cation conformational changes coincide with phase transitions in 1L systems.

Photoluminescence intensity varies significantly around transition temperatures.

Abstract

Halide double perovskites are an interesting alternative to Pb-containing counterparts as active materials in optoelectronic devices. Low-dimensional double perovskites are fabricated by introducing large organic cations, resulting in organic/inorganic architectures with one or more inorganic octahedral layers separated by organic cations. Here, we synthesize layered double perovskites based on 3D Cs2AgBiBr6 that consist of double (2L) or single (1L) inorganic octahedral layers, using ammonium cations of different size and chemical structure. Temperature-dependent Raman spectroscopy reveals phase transition signatures in both inorganic lattice and organic moieties by detecting variations in their vibrational modes. Changes in the conformational arrangement of the organic cations to an ordered state coincide with a phase transition in the 1L systems with the shortest ammonium moieties. Significant changes of photoluminescence intensity observed around the transition temperature suggest that optical properties may be deeply affected by the octahedral tilts emerging at the phase transition.