Issue 11, 2020

Anisotropic carrier diffusion in single MAPbI3 grains correlates to their twin domains

Abstract

Polycrystalline thin films and single crystals of hybrid perovskites – a material group successfully used for photovoltaic and optoelectronic applications – reportedly display heterogeneous charge carrier dynamics often attributed to grain boundaries or crystalline strain. Here, we locally resolved the carrier diffusion in large, isolated methylammonium lead iodide (MAPbI3) grains via spatial- and time-resolved photoluminescence microscopy. We found that the anisotropic carrier dynamics directly correlate with the arrangement of ferroelastic twin domains. Comparing diffusion constants parallel and perpendicular to the domains showed carriers diffuse around 50–60% faster along the parallel direction. Extensive piezoresponse force microscopy experiments on the nature of the domain pattern suggest that the diffusion anisotropy most likely originates from structural and electrical anomalies at ferroelastic domain walls. We believe that the domain walls act as shallow energetic barriers, which delay the transversal diffusion of carriers. Furthermore, we demonstrate a rearrangement of the domains via heat treatment above the cubic-tetragnal phase transition. Together with the previously reported strain engineering via external stress, our findings promise additional routes to tailor the directionality of the charge carrier diffusion in MAPbI3-based photovoltaics and optoelectronics as well as other ferroelastic materials for optoelectronic applications.

Graphical abstract: Anisotropic carrier diffusion in single MAPbI3 grains correlates to their twin domains

Supplementary files

Article information

Article type
Paper
Submitted
31 mar 2020
Accepted
02 jun 2020
First published
02 jun 2020
This article is Open Access
Creative Commons BY license

Energy Environ. Sci., 2020,13, 4168-4177

Anisotropic carrier diffusion in single MAPbI3 grains correlates to their twin domains

I. M. Hermes, A. Best, L. Winkelmann, J. Mars, S. M. Vorpahl, M. Mezger, L. Collins, H. Butt, D. S. Ginger, K. Koynov and S. A. L. Weber, Energy Environ. Sci., 2020, 13, 4168 DOI: 10.1039/D0EE01016B

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