Electronic properties and lattice vibrations are expected to be strongly correlated in metal-halide perovskites, due to the soft fluctuating nature of their crystal lattice. Thus, unveiling electron-phonon coupling dynamics upon ultrafast photoexcitation is necessary for understanding the optoelectronic behavior of the semiconductor. Here, we use impulsive vibrational spectroscopy to reveal vibrational modes of methylammonium lead-bromide perovskite under electronically resonant and non-resonant conditions. We identify two excited state coherent phonons at 89 and 106 cm-1, whose phases reveal a shift of the potential energy minimum upon ultrafast photocarrier generation. This indicates the transition to a new geometry, reached after approximately 90 fs, and fully equilibrated within the phonons lifetime of about 1 ps. Our results unambiguously prove that these modes drive the crystalline distortion occurring upon photo-excitation, demonstrating the presence of polaronic effects.

Probing femtosecond lattice displacement upon photo-carrier generation in lead halide perovskite / Batignani, Giovanni; Fumero, Giuseppe; Srimath Kandada, Ajay Ram; Cerullo, Giulio; Gandini, Marina; Ferrante, Carino; Petrozza, Annamaria; Scopigno, Tullio. - In: NATURE COMMUNICATIONS. - ISSN 2041-1723. - STAMPA. - 9:1(2018), p. 1971. [10.1038/s41467-018-04367-6]

Probing femtosecond lattice displacement upon photo-carrier generation in lead halide perovskite

Batignani, Giovanni;Fumero, Giuseppe;Ferrante, Carino;Scopigno, Tullio
2018

Abstract

Electronic properties and lattice vibrations are expected to be strongly correlated in metal-halide perovskites, due to the soft fluctuating nature of their crystal lattice. Thus, unveiling electron-phonon coupling dynamics upon ultrafast photoexcitation is necessary for understanding the optoelectronic behavior of the semiconductor. Here, we use impulsive vibrational spectroscopy to reveal vibrational modes of methylammonium lead-bromide perovskite under electronically resonant and non-resonant conditions. We identify two excited state coherent phonons at 89 and 106 cm-1, whose phases reveal a shift of the potential energy minimum upon ultrafast photocarrier generation. This indicates the transition to a new geometry, reached after approximately 90 fs, and fully equilibrated within the phonons lifetime of about 1 ps. Our results unambiguously prove that these modes drive the crystalline distortion occurring upon photo-excitation, demonstrating the presence of polaronic effects.
Chemistry (all); Biochemistry, Genetics and Molecular Biology (all); Physics and Astronomy (all)
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Probing femtosecond lattice displacement upon photo-carrier generation in lead halide perovskite / Batignani, Giovanni; Fumero, Giuseppe; Srimath Kandada, Ajay Ram; Cerullo, Giulio; Gandini, Marina; Ferrante, Carino; Petrozza, Annamaria; Scopigno, Tullio. - In: NATURE COMMUNICATIONS. - ISSN 2041-1723. - STAMPA. - 9:1(2018), p. 1971. [10.1038/s41467-018-04367-6]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1120736
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