Title: Intrinsic anion diffusivity in lead halide perovskites is facilitated by a soft lattice

Abstract

Facile ionic transport in lead halide perovskites plays a critical role in device performance. Understanding the microscopic origins of high ionic conductivities has been complicated by indirect measurements and sample microstructural heterogeneities. Here, we report the direct visualization of halide anion interdiffusion in CsPbCl₃–CsPbBr₃ single crystalline perovskite nanowire heterojunctions using wide-field and confocal photoluminescence measurements. The combination of nanoscale imaging techniques with these single crystalline materials allows us to measure intrinsic anionic lattice diffusivities, free from complications of microscale inhomogeneity. Halide diffusivities were found to be between 10^-13 and ~10^-12 cm²/second at about 100 °C, which are several orders of magnitudes lower than those reported in polycrystalline thin films. Spatially resolved photoluminescence lifetimes and surface potential measurements provide evidence of the central role of halide vacancies in facilitating ionic diffusion. Vacancy formation free energies computed from molecular simulation are small due to the easily deformable perovskite lattice, accounting for the high equilibrium vacancy concentration. Furthermore, molecular simulations suggest that ionic motion is facilitated by low-frequency lattice modes, resulting in low activation barriers for vacancy-mediated transport. This work elucidates the intrinsic solid-state ion diffusion mechanisms in this class of semisoft materials and offers guidelines for engineering materials with long-term stability inmore » functional devices.« less

Authors:

Lai, Minliang ^[1]; Obliger, Amael ^[1]; Lu, Dylan ^[2]; Kley, Christopher S. ^[1]; Bischak, Connor G. ^[1]; Kong, Qiao ^[1]; Lei, Teng ^[1]; Dou, Letian ^[3]; Ginsberg, Naomi S. ^[4]; Limmer, David T. ^[5]; Yang, Peidong ^[6]

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+ Show Author Affiliations

1. Department of Chemistry, University of California, Berkeley, CA 94720,
2. Department of Chemistry, University of California, Berkeley, CA 94720,, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,
3. Department of Chemistry, University of California, Berkeley, CA 94720,, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,, Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907,
4. Department of Chemistry, University of California, Berkeley, CA 94720,, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,, Department of Physics, University of California, Berkeley, CA 94720,, Kavli Energy NanoScience Institute, Berkeley, CA 94720,, Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,
5. Department of Chemistry, University of California, Berkeley, CA 94720,, Kavli Energy NanoScience Institute, Berkeley, CA 94720,, Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,
6. Department of Chemistry, University of California, Berkeley, CA 94720,, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,, Kavli Energy NanoScience Institute, Berkeley, CA 94720,, Department of Materials Science and Engineering, University of California, Berkeley, CA 94720

Publication Date:

Mon Nov 05 00:00:00 EST 2018

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1480900

Alternate Identifier(s):

OSTI ID: 1542340

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Published Article

Journal Name:

Proceedings of the National Academy of Sciences of the United States of America

Additional Journal Information:

Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Volume: 115 Journal Issue: 47; Journal ID: ISSN 0027-8424

Publisher:

Proceedings of the National Academy of Sciences

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; halide perovskite nanowire; anion diffusivity; nanoscale imaging; molecular simulation; soft lattice