Dynamic emission Stokes shift and liquid-like dielectric solvation of band edge carriers in lead-halide perovskites

Yinsheng Guo, Omer Yaffe, Trevor D. Hull, Jonathan S. Owen, David R. Reichman, Louis E. Brus

Research output: Contribution to journalArticlepeer-review

110 Scopus citations

Abstract

Lead-halide perovskites have emerged as promising materials for photovoltaic and optoelectronic applications. Their significantly anharmonic lattice motion, in contrast to conventional harmonic semiconductors, presents a conceptual challenge in understanding the genesis of their exceptional optoelectronic properties. Here we report a strongly temperature dependent luminescence Stokes shift in the electronic spectra of both hybrid and inorganic lead-bromide perovskite single crystals. This behavior stands in stark contrast to that exhibited by more conventional crystalline semiconductors. We correlate the electronic spectra with the anti-Stokes and Stokes Raman vibrational spectra. Dielectric solvation theories, originally developed for excited molecules dissolved in polar liquids, reproduce our experimental observations. Our approach, which invokes a classical Debye-like relaxation process, captures the dielectric response originating from the incipient anharmonicity of the LO phonon at about 20 meV (160 cm−1) in the lead-bromide framework. We reconcile this liquid-like model incorporating thermally-activated dielectric solvation with more standard solid-state theories of the emission Stokes shift in crystalline semiconductors.

Original languageEnglish
Article number1175
JournalNature Communications
Volume10
Issue number1
DOIs
StatePublished - 12 Mar 2019
Externally publishedYes

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Publisher Copyright:
© 2019, The Author(s).

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