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Different emissive states in the bulk and at the surface of methylammonium lead bromide perovskite revealed by two-photon micro-spectroscopy and lifetime measurements

Karki, Khadga Jung LU ; Pullerits, Tönu LU ; Zhang, Wei LU and Abdellah, Mohamed (2016) In APL Photonics 1.
Abstract
Two photon photoluminescence (2PPL) from single crystals of methyl ammonium lead bromide (CH3NH3PbBr3, MAPbBr3) is studied. We observe two components in the 2PPL spectra, which we assign to the photoluminescence
(PL) from the carrier recombination at the band edge and the recombination due to self-trapping of excitons. The PL Stokes shift of self-trapped excitons is about 100 meV from the band-gap energy. Our measurements show that about 15% of the total PL from regions about 40 μm deep inside the crystal is due to the emission from self-trapped exciton. This contribution increases to about 20% in the PL from the regions close to the surface. Time resolved measurements of 2PPL show that the PL due to band-edge recombination has a life... (More)
Two photon photoluminescence (2PPL) from single crystals of methyl ammonium lead bromide (CH3NH3PbBr3, MAPbBr3) is studied. We observe two components in the 2PPL spectra, which we assign to the photoluminescence
(PL) from the carrier recombination at the band edge and the recombination due to self-trapping of excitons. The PL Stokes shift of self-trapped excitons is about 100 meV from the band-gap energy. Our measurements show that about 15% of the total PL from regions about 40 μm deep inside the crystal is due to the emission from self-trapped exciton. This contribution increases to about 20% in the PL from the regions close to the surface. Time resolved measurements of 2PPL show that the PL due to band-edge recombination has a life time of about 8 ns while the PL lifetime of self-trapped excitons is in the order of 100 ns. Quantification of self-trapped excitons in the materials used in photovoltaics is important as such excitons hinder charge separation. As our results also show that an appreciable fraction of photo-generated carriers get trapped, the results are important in rational design of photovoltaics. On the other hand, our results also show that the self-trapped excitons broaden the emission spectrum, which may be useful in designing broadband light emitting devices.


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APL Photonics
volume
1
ISSN
2378-0967
DOI
10.1063/1.4948645
language
English
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yes
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d7052d97-6311-4ce8-af31-602fd44580a8
date added to LUP
2017-10-25 14:38:34
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@article{d7052d97-6311-4ce8-af31-602fd44580a8,
  abstract     = {Two photon photoluminescence (2PPL) from single crystals of methyl ammonium lead bromide (CH3NH3PbBr3, MAPbBr3) is studied. We observe two components in the 2PPL spectra, which we assign to the photoluminescence <br>
(PL) from the carrier recombination at the band edge and the recombination due to self-trapping of excitons. The PL Stokes shift of self-trapped excitons is about 100 meV from the band-gap energy. Our measurements show that about 15% of the total PL from regions about 40 μm deep inside the crystal is due to the emission from self-trapped exciton. This contribution increases to about 20% in the PL from the regions close to the surface. Time resolved measurements of 2PPL show that the PL due to band-edge recombination has a life time of about 8 ns while the PL lifetime of self-trapped excitons is in the order of 100 ns. Quantification of self-trapped excitons in the materials used in photovoltaics is important as such excitons hinder charge separation. As our results also show that an appreciable fraction of photo-generated carriers get trapped, the results are important in rational design of photovoltaics. On the other hand, our results also show that the self-trapped excitons broaden the emission spectrum, which may be useful in designing broadband light emitting devices.<br>
<br/><br/>},
  articleno    = {046103},
  author       = {Karki, Khadga Jung and Pullerits, Tönu and Zhang, Wei and Abdellah, Mohamed},
  issn         = {2378-0967},
  language     = {eng},
  series       = {APL Photonics},
  title        = {Different emissive states in the bulk and at the surface of methylammonium lead bromide perovskite revealed by two-photon micro-spectroscopy and lifetime measurements},
  url          = {http://dx.doi.org/10.1063/1.4948645},
  volume       = {1},
  year         = {2016},
}