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This content will become publicly available on September 28, 2018

Title: Polar Fluctuations in Metal Halide Perovskites Uncovered by Acoustic Phonon Anomalies

Solution-processable metal-halide perovskites (MHPs) offer great promise for efficient light harvesting and emitting devices due to their long carrier lifetime and superior carrier transport characteristics. Ferroelectric effects, a hallmark of traditional oxide perovskites, was proposed to be a mechanism to suppress carrier recombination and enhance charge transport in MHPs, but the existence and influence of such polar order is still of considerable debate. Here we performed transient reflection measurements on single crystals of both inorganic and organic-inorganic (hybrid) MHPs over a range of temperatures, and demonstrate significant phonon softening in the cubic phases close to the cubic-to-tetragonal phase transition temperatures. Such phonon softening indicates the formation of polar domains, which grow in size upon cooling and can persist in the low-temperature tetragonal and orthorhombic phases. Our results link the extraordinary electronic properties of MHPs to the spontaneous polarizations which can contribute to more efficient charge separation and characteristics of an indirect bandgap.
Authors:
ORCiD logo [1] ;  [1] ;  [2] ; ORCiD logo [3] ; ORCiD logo [3] ;  [3] ;  [1] ;  [1] ;  [1] ;  [3] ; ORCiD logo [3] ; ORCiD logo [2] ; ORCiD logo [1] ; ORCiD logo [4]
  1. Argonne National Lab. (ANL), Lemont, IL (United States)
  2. Northern Illinois Univ., DeKalb, IL (United States)
  3. Northwestern Univ., Evanston, IL (United States)
  4. Argonne National Lab. (ANL), Lemont, IL (United States); Northwestern Univ., Evanston, IL (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
ACS Energy Letters
Additional Journal Information:
Journal Volume: 2; Journal Issue: 10; Journal ID: ISSN 2380-8195
Publisher:
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22), Scientific User Facilities Division
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE
OSTI Identifier:
1402074