Tailoring Polaron Dimensions in Lead-Tin Hybrid Perovskites.
basic_science · Level V
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- Record sourced from PubMed, PMID 39189538.
- Also identified by DOI 10.1002/adma.202406109.
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Abstract
Charge carriers in the soft and polar perovskite lattice form so-called polaron quasiparticles, charge carriers dressed with a lattice deformation. The spatial extent of a polaron is governed by the material's electron-phonon interaction strength, which determines charge carrier effective mass, mobility, and the so-called Mott polaron density, that is, the maximum stable density of charge carriers that a perovskite can support. Despite its significance, controlling polaron dimensions has been challenging. Here, experimental substantial tuning of polaron dimensions is reported by lattice engineering, through Pb/Sn substitution in CH<sub>3</sub>NH<sub>3</sub>Sn<sub>x</sub>Pb<sub>1-x</sub>I<sub>3</sub>. The polaron dimension is deduced from the Mott polaron density, which can be composition-tuned over an order of magnitude, while charge carrier mobility occurs through band transport, and remains substantial across all compositions, ranging from 10 s to 100 s cm<sup>2</sup> V s<sup>-1</sup> at room temperature. The effective modulation of polaron size can be understood by considering the bond asymmetry after carrier injection as well as the random spatial distribution of Pb/Sn ions. This study underscores the potential for tailoring polaron dimensions, which is crucial for optimizing applications prioritizing either high charge carrier density or high mobility.