Park, Jeehong Huh, Soonsang Choi, Young Woo Kang, Donghee Kim, Minsoo Kim, Donghan Park, Soohyung Choi, Hyoung Joon Kim, Changyoung Yi, Yeonjin 2024-02-27T07:00:14Z 2024-02-27T07:00:14Z 2024-02-27 2024-03 1936-0851 https://pubs.kist.re.kr/handle/201004/149333 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 me, 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 (αR) of 0.28 eV ？. 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. English American Chemical Society Visualizing the Low-Energy Electronic Structure of Prototypical Hybrid Halide Perovskite through Clear Band Measurements Article 10.1021/acsnano.3c12587 1 ACS Nano, v.18, no.10, pp.7570 - 7579 ACS Nano 18 10 7570 7579 N scie scopus 001173674000001 Chemistry, Multidisciplinary Chemistry, Physical Nanoscience & Nanotechnology Materials Science, Multidisciplinary Chemistry Science & Technology - Other Topics Materials Science Article METHYLAMMONIUM LEAD IODIDE EFFECTIVE MASSES CH3NH3PBI3 CRYSTAL VALENCE Rashbaeffect band folding density functional theory angle-resolved photoelectron spectroscopy halide perovskites effective mass spin-resolvedphotoelectron spectroscopy