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Title: Ultrafast optical snapshots of hybrid perovskites reveal the origin of multiband electronic transitions

In this paper, connecting the complex electronic excitations of hybrid perovskites to their intricate organic-inorganic lattice structure has critical implications for energy conversion and optoelectronic technologies. Here we detail the multiband, multivalley electronic structure of a halide hybrid perovskite by measuring the absorption transients of a millimeter-scale-grain thin film as it undergoes a thermally controlled reversible tetragonal-to-orthogonal phase transition. Probing nearly single grains of this hybrid perovskite, we observe an unreported energy splitting (degeneracy lifting) of the high-energy 2.6 eV band in the tetragonal phase that further splits as the rotational degrees of freedom of the disordered CH 3NH 3 + molecules are reduced when the sample is cooled. This energy splitting drastically increases during an extended phase-transition coexistence region that persists from 160 to 120 K, becoming more pronounced in the orthorhombic phase. By tracking the temperature-dependent optical transition energies and using symmetry analysis that describes the evolution of electronic states from the tetragonal phase to the orthorhombic phase, we assign this energy splitting to the nearly degenerate transitions in the tetragonal phase from both the R- and M-point-derived states. Importantly, these assignments explain how momentum conservation effects lead to long hot-carrier lifetimes in the room-temperature tetragonal phase, withmore » faster hot-carrier relaxation when the hybrid perovskite structurally transitions to the orthorhombic phase due to enhanced scattering at the Γ point.« less
 [1] ;  [2] ;  [2] ;  [3] ;  [2] ; ORCiD logo [4]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN); Univ. of Alabama, Birmingham, AL (United States). Dept. of Physics
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. National Inst. of Applied Sciences (INSA)/CNRS, Rennes (France). Optical Functions for Information Technologies (FOTON)
  4. Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)
Publication Date:
Report Number(s):
BNL-204648-2018-JAAM; LA-UR-17-29873
Journal ID: ISSN 2469-9950; PRBMDO
Grant/Contract Number:
SC0012704; AC52-06NA25396; 08SPCE973; PEROPHOT 2015
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 96; Journal Issue: 19; Journal ID: ISSN 2469-9950
American Physical Society (APS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22) Scientific User Facilities Division; USDOE National Nuclear Security Administration (NNSA); USDOE Laboratory Directed Research and Development (LDRD) Program; Banque Populaire de l'Ouest Foundation
Country of Publication:
United States
36 MATERIALS SCIENCE; Material Science; Perovskites, electronic structure
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1410471; OSTI ID: 1460651