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"supertrap" at Work : Extremely Efficient Nonradiative Recombination Channels in MAPbI3 Perovskites Revealed by Luminescence Super-Resolution Imaging and Spectroscopy

Merdasa, Aboma LU ; Tian, Yuxi LU ; Camacho, Rafael; Dobrovolsky, Alexander LU ; Debroye, Elke; Unger, Eva L. LU ; Hofkens, Johan; Sundström, Villy LU and Scheblykin, Ivan G. LU (2017) In ACS Nano 11(6). p.5391-5404
Abstract

Organo-metal halide perovskites are some of the most promising materials for the new generation of low-cost photovoltaic and light-emitting devices. Their solution processability is a beneficial trait, although it leads to a spatial inhomogeneity of perovskite films with a variation of the trap state density at the nanoscale. Comprehending their properties using traditional spectroscopy therefore becomes difficult, calling for a combination with microscopy in order to see beyond the ensemble-averaged response. We studied photoluminescence (PL) blinking of micrometer-sized individual methylammonium lead iodide (MAPbI3) perovskite polycrystals, as well as monocrystalline microrods up to 10 μm long. We correlated their PL... (More)

Organo-metal halide perovskites are some of the most promising materials for the new generation of low-cost photovoltaic and light-emitting devices. Their solution processability is a beneficial trait, although it leads to a spatial inhomogeneity of perovskite films with a variation of the trap state density at the nanoscale. Comprehending their properties using traditional spectroscopy therefore becomes difficult, calling for a combination with microscopy in order to see beyond the ensemble-averaged response. We studied photoluminescence (PL) blinking of micrometer-sized individual methylammonium lead iodide (MAPbI3) perovskite polycrystals, as well as monocrystalline microrods up to 10 μm long. We correlated their PL dynamics with structure employing scanning electron and optical super-resolution microscopy. Combining super-resolution localization imaging and super-resolution optical fluctuation imaging (SOFI), we could detect and quantify preferential emitting regions in polycrystals exhibiting different types of blinking. We propose that blinking in MAPbI3 occurs by the activation/passivation of a "supertrap" which presumably is a donor-acceptor pair able to trap both electrons and holes. As such, nonradiative recombination via supertraps, in spite being present at a rather low concentrations (1012-1015 cm-3), is much more efficient than via all other defect states present in the material at higher concentrations (1016-1018 cm-3). We speculate that activation/deactivation of a supertrap occurs by its temporary dissociation into free donor and acceptor impurities. We found that supertraps are most efficient in structurally homogeneous and large MAPbI3 crystals where carrier diffusion is efficient, which may therefore pose limitations on the efficiency of perovskite-based devices.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
blinking, donor-acceptor pair, nonradiative recombination, perovskites, photoluminescence, super-resolution microscopy, traps
in
ACS Nano
volume
11
issue
6
pages
14 pages
publisher
The American Chemical Society
external identifiers
  • scopus:85021406818
  • wos:000404808000021
ISSN
1936-0851
DOI
10.1021/acsnano.6b07407
language
English
LU publication?
yes
id
8c8efd27-a599-4e71-9e9b-1a7365390a79
date added to LUP
2017-07-11 12:27:12
date last changed
2017-09-18 11:38:03
@article{8c8efd27-a599-4e71-9e9b-1a7365390a79,
  abstract     = {<p>Organo-metal halide perovskites are some of the most promising materials for the new generation of low-cost photovoltaic and light-emitting devices. Their solution processability is a beneficial trait, although it leads to a spatial inhomogeneity of perovskite films with a variation of the trap state density at the nanoscale. Comprehending their properties using traditional spectroscopy therefore becomes difficult, calling for a combination with microscopy in order to see beyond the ensemble-averaged response. We studied photoluminescence (PL) blinking of micrometer-sized individual methylammonium lead iodide (MAPbI<sub>3</sub>) perovskite polycrystals, as well as monocrystalline microrods up to 10 μm long. We correlated their PL dynamics with structure employing scanning electron and optical super-resolution microscopy. Combining super-resolution localization imaging and super-resolution optical fluctuation imaging (SOFI), we could detect and quantify preferential emitting regions in polycrystals exhibiting different types of blinking. We propose that blinking in MAPbI<sub>3</sub> occurs by the activation/passivation of a "supertrap" which presumably is a donor-acceptor pair able to trap both electrons and holes. As such, nonradiative recombination via supertraps, in spite being present at a rather low concentrations (10<sup>12</sup>-10<sup>15</sup> cm<sup>-3</sup>), is much more efficient than via all other defect states present in the material at higher concentrations (10<sup>16</sup>-10<sup>18</sup> cm<sup>-3</sup>). We speculate that activation/deactivation of a supertrap occurs by its temporary dissociation into free donor and acceptor impurities. We found that supertraps are most efficient in structurally homogeneous and large MAPbI<sub>3</sub> crystals where carrier diffusion is efficient, which may therefore pose limitations on the efficiency of perovskite-based devices.</p>},
  author       = {Merdasa, Aboma and Tian, Yuxi and Camacho, Rafael and Dobrovolsky, Alexander and Debroye, Elke and Unger, Eva L. and Hofkens, Johan and Sundström, Villy and Scheblykin, Ivan G.},
  issn         = {1936-0851},
  keyword      = {blinking,donor-acceptor pair,nonradiative recombination,perovskites,photoluminescence,super-resolution microscopy,traps},
  language     = {eng},
  month        = {06},
  number       = {6},
  pages        = {5391--5404},
  publisher    = {The American Chemical Society},
  series       = {ACS Nano},
  title        = {"supertrap" at Work : Extremely Efficient Nonradiative Recombination Channels in MAPbI<sub>3</sub> Perovskites Revealed by Luminescence Super-Resolution Imaging and Spectroscopy},
  url          = {http://dx.doi.org/10.1021/acsnano.6b07407},
  volume       = {11},
  year         = {2017},
}