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Title: Terahertz Emission from Hybrid Perovskites Driven by Ultrafast Charge Separation and Strong Electron-Phonon Coupling

Unusual photophysical properties of organic–inorganic hybrid perovskites have not only enabled exceptional performance in optoelectronic devices, but also led to debates on the nature of charge carriers in these materials. This study makes the first observation of intense terahertz (THz) emission from the hybrid perovskite methylammonium lead iodide (CH 3NH 3PbI 3) following photoexcitation, enabling an ultrafast probe of charge separation, hot–carrier transport, and carrier–lattice coupling under 1–sun–equivalent illumination conditions. Using this approach, the initial charge separation/transport in the hybrid perovskites is shown to be driven by diffusion and not by surface fields or intrinsic ferroelectricity. Diffusivities of the hot and band–edge carriers along the surface normal direction are calculated by analyzing the emitted THz transients, with direct implications for hot–carrier device applications. Furthermore, photogenerated carriers are found to drive coherent terahertz–frequency lattice distortions, associated with reorganizations of the lead–iodide octahedra as well as coupled vibrations of the organic and inorganic sublattices. This strong and coherent carrier–lattice coupling is resolved on femtosecond timescales and found to be important both for resonant and far–above–gap photoexcitation. As a result, this study indicates that ultrafast lattice distortions play a key role in the initial processes associated with charge transport.
Authors:
 [1] ;  [2] ;  [2] ;  [1] ;  [2] ;  [3] ;  [3] ;  [1] ;  [2] ;  [2] ;  [4]
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. Stanford Univ., Stanford, CA (United States)
  3. Pennsylvania State Univ., University Park, PA (United States)
  4. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States)
Publication Date:
Grant/Contract Number:
DGE-114747; SC0012375; AC02-76SF00515
Type:
Accepted Manuscript
Journal Name:
Advanced Materials
Additional Journal Information:
Journal Volume: 30; Journal Issue: 11; Journal ID: ISSN 0935-9648
Publisher:
Wiley
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; carrier-lattice coupling; charge separation; hybrid organic-inorganic perovskites; MAPbl3; THz emission; ultrafast structural dynamics
OSTI Identifier:
1457108
Alternate Identifier(s):
OSTI ID: 1417766