Slow Organic-to-Inorganic Sub-Lattice Thermalization in Methylammonium Lead Halide Perovskites Observed by Ultrafast Photoluminescence

Angela Y. Chang, Yi Ju Cho, Kuan Chen Chen, Chang Wen Chen, Alper Kinaci, Benjamin T. Diroll, Michael J. Wagner, Maria K Y Chan, Hao Wu Lin, Richard D Schaller

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Carrier dynamics in methylammonium lead halide (CH3NH3PbI3- xClx) perovskite thin films, of differing crystal morphology, are examined as functions of temperature and excitation wavelength. At room temperature, long-lived (>nanosecond) transient absorption signals indicate negligible carrier trapping. However, in measurements of ultrafast photoluminescence excited at 400 nm, a heretofore unexplained, large amplitude (50%-60%), 45 ps decay process is observed. This feature persists for temperatures down to the orthorhombic phase transition. Varying pump photon energy reveals that the fast, band-edge photoluminescence (PL) decay only appears for excitation ≥2.38 eV (520 nm), with larger amplitudes for higher pump energies. Lower photon-energy excitation yields slow dynamics consistent with negligible carrier trapping. Further, sub-bandgap two-photon pumping yields identical PL dynamics as direct absorption, signifying sensitivity to the total deposited energy and insensitivity to interfacial effects. Together with first principles electronic structure and ab initio molecular dynamics calculations, the results suggest the fast PL decay stems from excitation of high energy phonon modes associated with the organic sub-lattice that temporarily enhance wavefunction overlap within the inorganic component owing to atomic displacement, thereby transiently changing the PL radiative rate during thermalization. Hence, the fast PL decay relates a characteristic organic-to-inorganic sub-lattice equilibration timescale at optoelectronic-relevant excitation energies.

Original languageEnglish
JournalAdvanced Energy Materials
DOIs
Publication statusAccepted/In press - 2016

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Photoluminescence
Lead
Photons
Excitation energy
Pumps
Wave functions
Crystal lattices
Optoelectronic devices
Perovskite
Temperature
Electronic structure
Molecular dynamics
methylamine
Energy gap
Phase transitions
Thin films
Wavelength
Crystals

Keywords

  • Density functional theory
  • Hybrid perovskite
  • Transient absorption
  • Transient photoluminescence

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

Cite this

Slow Organic-to-Inorganic Sub-Lattice Thermalization in Methylammonium Lead Halide Perovskites Observed by Ultrafast Photoluminescence. / Chang, Angela Y.; Cho, Yi Ju; Chen, Kuan Chen; Chen, Chang Wen; Kinaci, Alper; Diroll, Benjamin T.; Wagner, Michael J.; Chan, Maria K Y; Lin, Hao Wu; Schaller, Richard D.

In: Advanced Energy Materials, 2016.

Research output: Contribution to journalArticle

Chang, Angela Y. ; Cho, Yi Ju ; Chen, Kuan Chen ; Chen, Chang Wen ; Kinaci, Alper ; Diroll, Benjamin T. ; Wagner, Michael J. ; Chan, Maria K Y ; Lin, Hao Wu ; Schaller, Richard D. / Slow Organic-to-Inorganic Sub-Lattice Thermalization in Methylammonium Lead Halide Perovskites Observed by Ultrafast Photoluminescence. In: Advanced Energy Materials. 2016.
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AU - Kinaci, Alper

AU - Diroll, Benjamin T.

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AB - Carrier dynamics in methylammonium lead halide (CH3NH3PbI3- xClx) perovskite thin films, of differing crystal morphology, are examined as functions of temperature and excitation wavelength. At room temperature, long-lived (>nanosecond) transient absorption signals indicate negligible carrier trapping. However, in measurements of ultrafast photoluminescence excited at 400 nm, a heretofore unexplained, large amplitude (50%-60%), 45 ps decay process is observed. This feature persists for temperatures down to the orthorhombic phase transition. Varying pump photon energy reveals that the fast, band-edge photoluminescence (PL) decay only appears for excitation ≥2.38 eV (520 nm), with larger amplitudes for higher pump energies. Lower photon-energy excitation yields slow dynamics consistent with negligible carrier trapping. Further, sub-bandgap two-photon pumping yields identical PL dynamics as direct absorption, signifying sensitivity to the total deposited energy and insensitivity to interfacial effects. Together with first principles electronic structure and ab initio molecular dynamics calculations, the results suggest the fast PL decay stems from excitation of high energy phonon modes associated with the organic sub-lattice that temporarily enhance wavefunction overlap within the inorganic component owing to atomic displacement, thereby transiently changing the PL radiative rate during thermalization. Hence, the fast PL decay relates a characteristic organic-to-inorganic sub-lattice equilibration timescale at optoelectronic-relevant excitation energies.

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