26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Optical probes of 2D perovskites and perovskite-inspired semiconductors

Not scheduled

1h 30m

Belinda Hutchinson Building (The University of Sydney )

Invited talk COMMAD - Optoelectronic and Microelectronic Materials and Devices Parallel sessions

Description

Metal-halide perovskites (MHPs) and “perovskite-inspired materials” (PIMs) have recently emerged as versatile materials for solar cells and photocatalytic applications. Ultrafast optical probes of photoconductivity dynamics are particularly useful here, uncovering the generation, localisation and ultimate recombination of charge carriers following photon absorption.

We examine charge transport in layered, two-dimensional metal halide perovskites (2DPs), whose electronic landscape is moderated through quantum confinement. We show that such layered semiconductors feature strongly suppressed out-of-plane diffusion coefficients near 10$^{−4}$ cm$^2$ s$^{−1}$, consistent with a diffusion anisotropy of about 4 orders of magnitude [1]. We reveal pronounced odd-even effects with carbon number of the Cx spacer cation in (Cx)$_2$PbI$_4$ 2DPs. Optical and transport properties, including absorption coefficients, photoluminescence energies and lifetimes, and excitation diffusion dynamics depend strongly on carbon number parity [2,3]. Out-of-plane diffusion of photoexcitations displays an opposite odd–even trend to in-plane charge-carrier mobility, causing a pronounced odd–even modulation of the thin-film mobility anisotropy [3].

We further report on charge-carrier conduction in new metal-halide based PIMs, which have been shown to exhibit dynamic transitions from large to small polaronic states. We demonstrate that in Mixed-metal chalcohalides (A$_2$BCh$_2$X$_3$) charge-carrier localisation can be overcome through judicious chemical substitution substitution of the M(II) cation on the A-site [4]. We show that a shift in lattice symmetry from the lower-symmetry monoclinic P2$_1$/c phase in Pb$_2$SbS$_2$I$_3$ to the higher-symmetry orthorhombic Cmcm phase in Sn$_2$SbS$_2$I$_3$ fully suppresses such self-localisation as a result of higher electronic dimensionality.

[1] J. Du, … , L. M. Herz, Adv. Func. Mater. 35, 2421817 (2025).
[2] M. Choghaei, … , S. Olthof, Journal of Materials Chemistry A 13, 18935 (2025).
[3] J. Du, … , L. M. Herz, ACS Nano 20, 15706 (2026).
[4] B. C. Mackintosh, … , L. M. Herz, JACS, DOI: 10.1021/jacs.6c05142 (2026).