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- A nd 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.
| Original language | English |
|---|---|
| Pages (from-to) | 4168-4177 |
| Number of pages | 10 |
| Journal | Energy and Environmental Science |
| Volume | 13 |
| Issue number | 11 |
| DOIs | |
| State | Published - Nov 2020 |
Funding
I. M. H. acknowledges ERC Grant No. 340391 SuPro for funding. D. S. G. and S. M. H. acknowledge support from the DOE (DE-SC0013957). LDV-PFM was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. PFM during heat treatment was conducted at the Molecular Analysis Facility, a National Nanotechnology Coordinated Infrastructure site at the University of Washington, which is supported in part by the National Science Foundation (Grant ECC-1542101), the University of Washington, the Molecular Engineering & Sciences Institute, the Clean Energy Institute, and the National Institutes of Health. We thank Rüdiger Berger and Denis Andrienko for helpful discussions. Open Access funding provided by the Max Planck Society.
