Visualizing the Low-Energy Electronic Structure of Prototypical Hybrid Halide Perovskite through Clear Band Measurements.
basic_science · Level V
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- Record sourced from PubMed, PMID 38377437.
- Also identified by DOI 10.1021/acsnano.3c12587.
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Abstract
Organic-inorganic hybrid perovskites (OIHPs) are a promising class of materials that rival conventional semiconductors in various optoelectronic applications. However, unraveling the precise nature of their low-energy electronic structures continues to pose a significant challenge, primarily due to the absence of clear band measurements. Here, we investigate the low-energy electronic structure of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> (MAPI<sub>3</sub>) using angle-resolved photoelectron spectroscopy combined with <i>ab initio</i> density functional theory. We successfully visualize the electronic structure of MAPI<sub>3</sub> near the bulk valence band maximum by using a laboratory photon source (He I<sub>α</sub>, 21.2 eV) at low temperature and explore its fundamental properties. The observed valence band exhibits a highly isotropic and parabolic band characterized by small effective masses of 0.20-0.21 <i>m</i><sub>e</sub>, without notable spectral signatures associated with a large polaron or the Rashba effect, subjects that are intensely debated in the literature. Concurrently, our spin-resolved measurements directly disprove the giant Rashba scenario previously suggested in a similar perovskite compound by establishing an upper limit for the Rashba parameter (<i>α</i><sub>R</sub>) of 0.28 eV Å. Our results unveil the unusually complex nature of the low-energy electronic structure of OIHPs, thereby advancing our fundamental understanding of this important class of materials.