Halide Mixing Inhibits Exciton Transport in Two-Dimensional Perovskites Despite Phase Purity
Michael Seitz a b c, Marc Melendez a, Peyton York d, Daniel Kurtz b, Alvaro Magdaleno a, Nerea Alcazar a, Mahesh Gangishetty b d, Rafael Delgado-Buscalioni a, Daniel Congreve b c, Ferry Prins a
a Universidad Autonoma de Madrid, ES, Spain
b Rowland Institute at Harvard, Massachusetts, US, Edwin H Land Boulevard, 100, Cambridge, United States
c Department of Electrical Engineering, Stanford University, United States
d Mississippi State University, Locksley Way, 201, Starkville, United States
Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting 2021 (NFM21)
#SPMEn21. Visualising nanoscale phenomena in functional materials
Online, Spain, 2021 October 18th - 22nd
Organizers: Stefan Weber, Brian Rodriguez and Juliane Borchert
Contributed talk, Ferry Prins, presentation 089
DOI: https://doi.org/10.29363/nanoge.nfm.2021.089
Publication date: 23rd September 2021

Metal-halide perovskites are a versatile material platform for light-harvesting and light-emitting applications as their variable chemical composition allows the optoelectronic properties to be tailored to specific applications. Halide mixing is one of the most powerful techniques to tune the optical bandgap of metal-halide perovskites across wide spectral ranges. However, halide mixing has commonly been observed to result in phase segregation, which reduces excited-state transport and limits device performance. While the current emphasis lies on the development of strategies to prevent phase segregation, it remains unclear how halide mixing may affect excited-state transport even if phase purity is maintained.

In this work, we use transient photoluminescence microscopy to study excitonic excited-state transport in phase pure mixed-halide 2D perovskites. We show that, despite phase purity, halide mixing inhibits exciton transport in these materials. We find a significant reduction even for relatively low alloying concentrations, with bromide-rich perovskites being particularly sensitive to the introduction of iodide ions. Performing Brownian dynamics simulations, we are able to reproduce our experimental results and attribute the decrease in diffusivity to the energetically disordered potential landscape that arises due to the intrinsic random distribution of alloying sites. Our results suggest that even in the absence of phase segregation, halide mixing may still impact carrier transport due to the local intrinsic inhomogeneities in the energy landscape.

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