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Title: Local polar fluctuations in lead halide perovskite crystals

Abstract

Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations that inhibit carrier recombination. We combine low-frequency Raman scattering with first-principles molecular dynamics (MD) to study the fundamental nature of these local polar fluctuations. Our observations of a strong central peak in the cubic phase of both hybrid (CH 3NH 3PbBr 3) and all-inorganic (CsPbBr 3) lead-halide perovskites show that anharmonic, local polar fluctuations are intrinsic to the general lead-halide perovskite structure, and not unique to the dipolar organic cation. Furthermore, MD simulations indicate that head-to-head Cs motion coupled to Br face expansion, occurring on a few hundred femtosecond time scale, drives the local polar fluctuations in CsPbBr 3.

Authors:
 [1];  [1];  [2];  [3];  [1];  [4];  [2];  [5];  [3];  [6];  [1];  [2];  [7];  [1]
  1. Columbia Univ., New York, NY (United States)
  2. Univ. of Pennsylvania, Philadelphia, PA (United States)
  3. Weizmann Institute of Science, Rehovoth (Israel)
  4. Argonne National Lab. (ANL), Argonne, IL (United States)
  5. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  6. Argonne National Lab. (ANL), Argonne, IL (United States); Northwestern Univ., Evanston, IL (United States)
  7. Columbia Univ., New York, NY (United States); Univ. Federal de Minas Gerais, Belo Horizonte (Brazil)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1352545
Alternate Identifier(s):
OSTI ID: 1349148
Grant/Contract Number:
SC0001085; IOF-622653; N00014-14-1-0761; N00014-12-1-1033; FG02-07ER46431; J3608-N20; NA0002522; AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 118; Journal Issue: 13; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; 36 MATERIALS SCIENCE; local polar fluctuations; hybrid perovskites; low frequency Raman scattering; molecular dynamics; radiation detection; Central peak

Citation Formats

Yaffe, Omer, Guo, Yinsheng, Tan, Liang Z., Egger, David A., Hull, Trevor, Stoumpos, Constantinos C., Zheng, Fan, Heinz, Tony F., Kronik, Leeor, Kanatzidis, Mercouri G., Owen, Jonathan S., Rappe, Andrew M., Pimenta, Marcos A., and Brus, Louis E. Local polar fluctuations in lead halide perovskite crystals. United States: N. p., 2017. Web. doi:10.1103/PhysRevLett.118.136001.
Yaffe, Omer, Guo, Yinsheng, Tan, Liang Z., Egger, David A., Hull, Trevor, Stoumpos, Constantinos C., Zheng, Fan, Heinz, Tony F., Kronik, Leeor, Kanatzidis, Mercouri G., Owen, Jonathan S., Rappe, Andrew M., Pimenta, Marcos A., & Brus, Louis E. Local polar fluctuations in lead halide perovskite crystals. United States. doi:10.1103/PhysRevLett.118.136001.
Yaffe, Omer, Guo, Yinsheng, Tan, Liang Z., Egger, David A., Hull, Trevor, Stoumpos, Constantinos C., Zheng, Fan, Heinz, Tony F., Kronik, Leeor, Kanatzidis, Mercouri G., Owen, Jonathan S., Rappe, Andrew M., Pimenta, Marcos A., and Brus, Louis E. Tue . "Local polar fluctuations in lead halide perovskite crystals". United States. doi:10.1103/PhysRevLett.118.136001. https://www.osti.gov/servlets/purl/1352545.
@article{osti_1352545,
title = {Local polar fluctuations in lead halide perovskite crystals},
author = {Yaffe, Omer and Guo, Yinsheng and Tan, Liang Z. and Egger, David A. and Hull, Trevor and Stoumpos, Constantinos C. and Zheng, Fan and Heinz, Tony F. and Kronik, Leeor and Kanatzidis, Mercouri G. and Owen, Jonathan S. and Rappe, Andrew M. and Pimenta, Marcos A. and Brus, Louis E.},
abstractNote = {Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations that inhibit carrier recombination. We combine low-frequency Raman scattering with first-principles molecular dynamics (MD) to study the fundamental nature of these local polar fluctuations. Our observations of a strong central peak in the cubic phase of both hybrid (CH3NH3PbBr3) and all-inorganic (CsPbBr3) lead-halide perovskites show that anharmonic, local polar fluctuations are intrinsic to the general lead-halide perovskite structure, and not unique to the dipolar organic cation. Furthermore, MD simulations indicate that head-to-head Cs motion coupled to Br face expansion, occurring on a few hundred femtosecond time scale, drives the local polar fluctuations in CsPbBr3.},
doi = {10.1103/PhysRevLett.118.136001},
journal = {Physical Review Letters},
number = 13,
volume = 118,
place = {United States},
year = {Tue Mar 28 00:00:00 EDT 2017},
month = {Tue Mar 28 00:00:00 EDT 2017}
}

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  • Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations that inhibit carrier recombination. We combine low-frequency Raman scattering with first-principles molecular dynamics (MD) to study the fundamental nature of these local polar fluctuations. Our observations of a strong central peak in the cubic phase of both hybrid (CH3NH3PbBr3) and all-inorganic (CsPbBr3) leadhalide perovskites show that anharmonic, local polar fluctuations are intrinsic to the general lead-halide perovskite structure, and not unique to the dipolar organic cation. MD simulations indicate that head-tohead Cs motion coupledmore » to Br face expansion, occurring on a few hundred femtosecond time scale, drives the local polar fluctuations in CsPbBr3.« less
  • The ease of processing hybrid organic–inorganic perovskite (HOIPs) films, belonging to a material class with composition ABX 3, from solution and at mild temperatures promises their use in deformable technologies, including flexible photovoltaic devices, sensors, and displays. To successfully apply these materials in deformable devices, knowledge of their mechanical response to dynamic strain is necessary. The authors elucidate the time- and rate-dependent mechanical properties of HOIPs and an inorganic perovskite (IP) single crystal by measuring nanoindentation creep and stress relaxation. The observation of pop-in events and slip bands on the surface of the indented crystals demonstrate dislocation-mediated plastic deformation. Themore » magnitudes of creep and relaxation of both HOIPs and IPs are similar, negating prior hypothesis that the presence of organic A-site cations alters the mechanical response of these materials. Moreover, these samples exhibit a pronounced increase in creep, and stress relaxation as a function of indentation rate whose magnitudes reflect differences in the rates of nucleation and propagation of dislocations within the crystal structures of HOIPs and IP. In conclusion, this contribution provides understanding that is critical for designing perovskite devices capable of withstanding mechanical deformations.« less
  • Owing to its ideal semiconducting band gap and good carrier transport properties, the fully inorganic perovskite CsSnI 3 has been proposed as a visible-light absorber for photovoltaic (PV) applications. However, compared to the organic inorganic lead halide perovskite CH 3NH 3PbI 3, CsSnI 3 solar cells display very low energy conversion efficiency. In this work, we propose a potential route to improve the PV properties of CsSnI 3. Using first-principles calculations, we examine the crystal structures and electronic properties of CsSnI 3, including its structural polymorphs. Next, we purposefully order Cs and Rb cations on the A site to createmore » the double perovskite (CsRb)Sn 2I 6. We find that a stable ferroelectric polarization arises from the nontrivial coupling between polar displacements and octahedral rotations of the SnI 6 network. These ferroelectric double perovskites are predicted to have energy band gaps and carrier effective masses similar to those of CsSnI 3. More importantly, unlike nonpolar CsSnI 3, the electric polarization present in ferroelectric (CsRb)Sn 2I 6 can effectively separate the photoexcited carriers, leading to novel ferroelectric PV materials with,potentially enhanced energy conversion efficiency.« less