Visualizing the Low-Energy Electronic Structure of Prototypical Hybrid Halide Perovskite through Clear Band Measurements

• Published in: ACS Nano Vol. 18; no. 10; pp. 7570 - 7579
• Main Authors: Park, Jeehong, Huh, Soonsang, Choi, Young Woo, Kang, Donghee, Kim, Minsoo, Kim, Donghan, Park, Soohyung, Choi, Hyoung Joon, Kim, Changyoung, Yi, Yeonjin
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 12.03.2024; American Chemical Society (ACS)
• Subjects: Rashba effect; angle-resolved photoelectron spectroscopy; effective mass; density functional theory; band folding; halide perovskites; spin-resolved photoelectron spectroscopy
• ISSN: 1936-0851; 1936-086X; 1936-086X
• DOI: 10.1021/acsnano.3c12587

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 CH3NH3PbI3 (MAPI3) using angle-resolved photoelectron spectroscopy combined with ab initio density functional theory. We successfully visualize the electronic structure of MAPI3 near the bulk valence band maximum by using a laboratory photon source (He Iα, 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 m e, 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 (α R) 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.