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Investigating the Role of the Organic Cation in Formamidinium Lead Iodide Perovskite Using Ultrafast Spectroscopy

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Investigating the Role of the Organic Cation in Formamidinium Lead Iodide Perovskite Using Ultrafast Spectroscopy. / Taylor, Victoria; Tiwari, Devendra; Duchi, Marta; Donaldson, Paul M.; Clark, Ian P.; Fermin, David; Oliver, Thomas A A.

In: Journal of Physical Chemistry Letters, Vol. 9, No. 4, 15.02.2018, p. 895-901.

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@article{7998a382bacc41678d414fbad685b8be,
title = "Investigating the Role of the Organic Cation in Formamidinium Lead Iodide Perovskite Using Ultrafast Spectroscopy",
abstract = "Organic cation rotation in hybrid organic−inorganic lead halide perovskites has previously been associated with low charge recombination rates and (anti)ferroelectric domain formation. Two-dimensional infrared spectroscopy (2DIR) was used to directly measure 470 ± 50 fs and 2.8 ± 0.5 ps time constants associated with the reorientation of formamidinium cations (FA+, NH2CHNH2+) in formamidinium lead iodide perovskite thin films. Molecular dynamics simulations reveal the FA+ agitates about an equilibrium position, with NH2 groups pointing at opposite faces of the inorganic lattice cube, and undergoes 90° flips on picosecond time scales. Time-resolved infrared measurements revealed a prominent vibrational transient feature arising from a vibrational Stark shift: photogenerated charge carriers increase the internal electric field of perovskite thin films, perturbing the FA+ antisymmetric stretching vibrational potential, resulting in an observed 5 cm-1 shift. Our 2DIR results provide the first direct measurement of FA+ rotation inside thin perovskite films, and cast significant doubt on the presence of long-lived (anti)ferroelectric domains, which the observed low charge recombination rates have been attributed to.",
author = "Victoria Taylor and Devendra Tiwari and Marta Duchi and Donaldson, {Paul M.} and Clark, {Ian P.} and David Fermin and Oliver, {Thomas A A}",
year = "2018",
month = "2",
day = "15",
doi = "10.1021/acs.jpclett.7b03296",
language = "English",
volume = "9",
pages = "895--901",
journal = "Journal of Physical Chemistry Letters",
issn = "1948-7185",
publisher = "American Chemical Society",
number = "4",

}

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TY - JOUR

T1 - Investigating the Role of the Organic Cation in Formamidinium Lead Iodide Perovskite Using Ultrafast Spectroscopy

AU - Taylor, Victoria

AU - Tiwari, Devendra

AU - Duchi, Marta

AU - Donaldson, Paul M.

AU - Clark, Ian P.

AU - Fermin, David

AU - Oliver, Thomas A A

PY - 2018/2/15

Y1 - 2018/2/15

N2 - Organic cation rotation in hybrid organic−inorganic lead halide perovskites has previously been associated with low charge recombination rates and (anti)ferroelectric domain formation. Two-dimensional infrared spectroscopy (2DIR) was used to directly measure 470 ± 50 fs and 2.8 ± 0.5 ps time constants associated with the reorientation of formamidinium cations (FA+, NH2CHNH2+) in formamidinium lead iodide perovskite thin films. Molecular dynamics simulations reveal the FA+ agitates about an equilibrium position, with NH2 groups pointing at opposite faces of the inorganic lattice cube, and undergoes 90° flips on picosecond time scales. Time-resolved infrared measurements revealed a prominent vibrational transient feature arising from a vibrational Stark shift: photogenerated charge carriers increase the internal electric field of perovskite thin films, perturbing the FA+ antisymmetric stretching vibrational potential, resulting in an observed 5 cm-1 shift. Our 2DIR results provide the first direct measurement of FA+ rotation inside thin perovskite films, and cast significant doubt on the presence of long-lived (anti)ferroelectric domains, which the observed low charge recombination rates have been attributed to.

AB - Organic cation rotation in hybrid organic−inorganic lead halide perovskites has previously been associated with low charge recombination rates and (anti)ferroelectric domain formation. Two-dimensional infrared spectroscopy (2DIR) was used to directly measure 470 ± 50 fs and 2.8 ± 0.5 ps time constants associated with the reorientation of formamidinium cations (FA+, NH2CHNH2+) in formamidinium lead iodide perovskite thin films. Molecular dynamics simulations reveal the FA+ agitates about an equilibrium position, with NH2 groups pointing at opposite faces of the inorganic lattice cube, and undergoes 90° flips on picosecond time scales. Time-resolved infrared measurements revealed a prominent vibrational transient feature arising from a vibrational Stark shift: photogenerated charge carriers increase the internal electric field of perovskite thin films, perturbing the FA+ antisymmetric stretching vibrational potential, resulting in an observed 5 cm-1 shift. Our 2DIR results provide the first direct measurement of FA+ rotation inside thin perovskite films, and cast significant doubt on the presence of long-lived (anti)ferroelectric domains, which the observed low charge recombination rates have been attributed to.

U2 - 10.1021/acs.jpclett.7b03296

DO - 10.1021/acs.jpclett.7b03296

M3 - Letter

VL - 9

SP - 895

EP - 901

JO - Journal of Physical Chemistry Letters

JF - Journal of Physical Chemistry Letters

SN - 1948-7185

IS - 4

ER -