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Title: Shallow trapping vs. deep polarons in a hybrid lead halide perovskite, CH 3NH 3PbI 3

Abstract

There has been considerable speculation over the nature of charge carriers in organic–inorganic hybrid perovskites, i.e., whether they are free and band-like, or they are prone to self-trapping via short range deformation potentials. Unusually long minority-carrier diffusion lengths and moderate-to-low mobilities, together with relatively few deep defects add to their intrigue. Here we implement density functional methods to investigate the room-temperature, tetragonal phase of CH 3NH 3PbI 3. We compare charge localization behavior at shallow levels and associated lattice relaxation versus those at deep polaronic states. The shallow level originates from screened Coulomb interaction between the perturbed host and an excited electron or hole. The host lattice has a tendency towards forming these shallow traps where the electron or hole is localized not too far from the band edge. In contrast, there is a considerable potential barrier that must be overcome in order to initiate polaronic hole trapping. The formation of a hole polaron (I 2 - center) involves strong lattice relaxation, including large off-center displacement of the organic cation, CH 3NH 3 +. This type of deep polaron is energetically unfavorable, and active shallow traps are expected to shape the carrier dynamics in this material.

Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory-National Energy Research Scientific Computing Center
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1492431
DOE Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Physical Chemistry Chemical Physics. PCCP (Print)
Additional Journal Information:
Journal Volume: 19; Journal Issue: 40; Journal ID: ISSN 1463-9076
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English

Citation Formats

None, None. Shallow trapping vs. deep polarons in a hybrid lead halide perovskite, CH3NH3PbI3. United States: N. p., 2017. Web. doi:10.1039/c7cp04417h.
None, None. Shallow trapping vs. deep polarons in a hybrid lead halide perovskite, CH3NH3PbI3. United States. https://doi.org/10.1039/c7cp04417h
None, None. Sun . "Shallow trapping vs. deep polarons in a hybrid lead halide perovskite, CH3NH3PbI3". United States. https://doi.org/10.1039/c7cp04417h.
@article{osti_1492431,
title = {Shallow trapping vs. deep polarons in a hybrid lead halide perovskite, CH3NH3PbI3},
author = {None, None},
abstractNote = {There has been considerable speculation over the nature of charge carriers in organic–inorganic hybrid perovskites, i.e., whether they are free and band-like, or they are prone to self-trapping via short range deformation potentials. Unusually long minority-carrier diffusion lengths and moderate-to-low mobilities, together with relatively few deep defects add to their intrigue. Here we implement density functional methods to investigate the room-temperature, tetragonal phase of CH3NH3PbI3. We compare charge localization behavior at shallow levels and associated lattice relaxation versus those at deep polaronic states. The shallow level originates from screened Coulomb interaction between the perturbed host and an excited electron or hole. The host lattice has a tendency towards forming these shallow traps where the electron or hole is localized not too far from the band edge. In contrast, there is a considerable potential barrier that must be overcome in order to initiate polaronic hole trapping. The formation of a hole polaron (I2- center) involves strong lattice relaxation, including large off-center displacement of the organic cation, CH3NH3+. This type of deep polaron is energetically unfavorable, and active shallow traps are expected to shape the carrier dynamics in this material.},
doi = {10.1039/c7cp04417h},
url = {https://www.osti.gov/biblio/1492431}, journal = {Physical Chemistry Chemical Physics. PCCP (Print)},
issn = {1463-9076},
number = 40,
volume = 19,
place = {United States},
year = {2017},
month = {1}
}

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