Imaging the Terahertz Nanoscale Conductivity of Polycrystalline CsPbBr<sub>3</sub> Perovskite Thin Films.
basic_science · Level V
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- Record sourced from PubMed, PMID 36862532.
- Also identified by DOI 10.1021/acs.nanolett.2c03214.
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Abstract
Terahertz (THz) radiation is a valuable tool to investigate the electronic properties of lead halide perovskites (LHPs). However, attaining high-resolution information remains elusive, as the diffraction-limited spatial resolution (∼300 μm) of conventional THz methods prevents a direct analysis of microscopic effects. Here, we employ THz scattering scanning near-field optical microscopy (THz-sSNOM) for nanoscale imaging of cesium lead bromide (CsPbBr<sub>3</sub>) thin films down to the single grain level at 600 GHz. Adopting a scattering model, we are able to derive the local THz nanoscale conductivity in a contact-free fashion. Increased THz near-field signals at CsPbBr<sub>3</sub> grain boundaries complemented by correlative transmission electron microscopy-energy-dispersive X-ray spectroscopy elemental analysis point to the formation of halide vacancies (V<sub>Br</sub>) and Pb-Pb bonds, which induce charge carrier trapping and can lead to nonradiative recombination. Our study establishes THz-sSNOM as a powerful THz nanoscale analysis platform for thin-film semiconductors such as LHPs.