Landé g ‐factor Spectroscopy of Rydberg Excitons and Band Edge Electron‐Hole Pairs in Two‐Dimensional Hybrid Lead Halide Perovskite Films

We present a comprehensive investigation of the Landé g ‐factor of the exciton Rydberg series and band‐edge electron‐hole pairs in two‐dimensional phenethylammonium lead iodide (PEPI) films using magnetic circular dichroism (MCD) spectroscopy. At low magnetic field ( B < 0.5 T), we observe a sizable difference of 15%–20% between the effective g ‐factors of the 1s exciton and that of the higher energy Rydberg excitons, which overlap with the interband (IB) electron‐hole (e‐h) pair transitions at the band‐edge (labeled here as the “2s+” band). At T = 3 K, we obtained g 1 s = 1.86 ± 0.15 and g 2 s + = 2.33 ± 0.15. These results demonstrate that the exciton g ‐factor is smaller than the sum of the individual electron and hole band edge g ‐factors, namely g exciton < g e + g h = g IB . The experimental results are rationalized by theoretical calculations of the g ‐factors using a multiband effective‐mass model that includes the electron‐hole interaction for the different exciton states. It is shown that with the decreasing spatial extent of the exciton wavefunction, the exciton g ‐factor also decreases. At B > 10 T, the interband Landau level transition (N = 1) extrapolates to the bandgap value in PEPI at E g = 2.62 ± 0.016 eV, providing further evidence of the formation of Rydberg excitons.