Electroabsorption Spectroscopy Measurements of the Exciton Binding Energy, Electron−Hole Reduced Effective Mass, and Band Gap in the Perovskite CH3NH3PbI3

We use electroabsorption (EA) spectroscopy to measure the exciton binding energy (EB), electron−hole reduced effective mass (μ), and one-electron band gap (Eg) at the fundamental absorption edge of the hybrid organic− inorganic perovskite CH3NH3PbI3 in its tetragonal phase at 300 K. By studying the second-harmonic EA spectra at the fundamental absorption edge we establish that the roomtemperature EA response in CH3NH3PbI3 follows the low-field Franz−Keldysh−Aspnes (FKA) effect. Following FKA analysis we find that μ = 0.12 ± 0.03m0, EB = 7.4 meV, and Eg = 1.633 eV. Our results provide direct experimental evidence that at room temperature primary transitions occurring in CH3NH3PbI3 can essentially be described in terms of free carrier generation.