Weak dispersion of exciton Landé factor with band gap energy in lead halide perovskites: Approximate compensation of the electron and hole dependences

• Published in: arXiv.org 2023-01
• Main Authors: Kopteva, N E, Yakovlev, D R, Kirstein, E, Zhukov, E A, Kudlacik, D, Kalitukha, I V, Sapega, V F, Dirin, D N, Kovalenko, M V, Baumann, A, Höcker, J, Dyakonov, V, Crooker, S A, Bayer, M
• Format: Article
• Language: English
• Subjects: Anisotropy; Bromine; Energy gap; Excitons; Halogens; Lead compounds; Liquid helium; Magnetic fields; Metal halides; Optoelectronics; Parameters; Perovskites
• ISSN: 2331-8422

The photovoltaic and optoelectronic properties of lead halide perovskite semiconductors are controlled by excitons, so that investigation of their fundamental properties is of critical importance. The exciton Landé or g-factor g_X is the key parameter, determining the exciton Zeeman spin splitting in magnetic fields. The exciton, electron and hole carrier g-factors provide information on the band structure, including its anisotropy, and the parameters contributing to the electron and hole effective masses. We measure g_X by reflectivity in magnetic fields up to 60 T for lead halide perovskite crystals. The materials band gap energies at a liquid helium temperature vary widely across the visible spectral range from 1.520 up to 3.213 eV in hybrid organic-inorganic and fully inorganic perovskites with different cations and halogens: FA_{0.9}Cs_{0.1}PbI_{2.8}Br_{0.2], MAPbI_{3}, FAPbBr_{3}, CsPbBr_{3}, and MAPb(Br_{0.05}Cl_{0.95})_{3}. We find the exciton g-factors to be nearly constant, ranging from +2.3 to +2.7. Thus, the strong dependences of the electron and hole g-factors on the band gap roughly compensate each other when combining to the exciton g-factor. The same is true for the anisotropies of the carrier g-factors, resulting in a nearly isotropic exciton g-factor. The experimental data are compared favorably with model calculation results.