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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 CsPbCl 3 –CsPbBr 3 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 cm 2 /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 guidelinesmore » for engineering materials with long-term stability in functional devices.« less

Authors:
; ; ; ; ; ; ; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1480900
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article: 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

Citation Formats

Lai, Minliang, Obliger, Amael, Lu, Dylan, Kley, Christopher S., Bischak, Connor G., Kong, Qiao, Lei, Teng, Dou, Letian, Ginsberg, Naomi S., Limmer, David T., and Yang, Peidong. Intrinsic anion diffusivity in lead halide perovskites is facilitated by a soft lattice. United States: N. p., 2018. Web. doi:10.1073/pnas.1812718115.
Lai, Minliang, Obliger, Amael, Lu, Dylan, Kley, Christopher S., Bischak, Connor G., Kong, Qiao, Lei, Teng, Dou, Letian, Ginsberg, Naomi S., Limmer, David T., & Yang, Peidong. Intrinsic anion diffusivity in lead halide perovskites is facilitated by a soft lattice. United States. doi:10.1073/pnas.1812718115.
Lai, Minliang, Obliger, Amael, Lu, Dylan, Kley, Christopher S., Bischak, Connor G., Kong, Qiao, Lei, Teng, Dou, Letian, Ginsberg, Naomi S., Limmer, David T., and Yang, Peidong. Mon . "Intrinsic anion diffusivity in lead halide perovskites is facilitated by a soft lattice". United States. doi:10.1073/pnas.1812718115.
@article{osti_1480900,
title = {Intrinsic anion diffusivity in lead halide perovskites is facilitated by a soft lattice},
author = {Lai, Minliang and Obliger, Amael and Lu, Dylan and Kley, Christopher S. and Bischak, Connor G. and Kong, Qiao and Lei, Teng and Dou, Letian and Ginsberg, Naomi S. and Limmer, David T. and Yang, Peidong},
abstractNote = {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 CsPbCl 3 –CsPbBr 3 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 cm 2 /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 in functional devices.},
doi = {10.1073/pnas.1812718115},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 47,
volume = 115,
place = {United States},
year = {Mon Nov 05 00:00:00 EST 2018},
month = {Mon Nov 05 00:00:00 EST 2018}
}

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Works referenced in this record:

Sequential deposition as a route to high-performance perovskite-sensitized solar cells
journal, July 2013

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