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 (E-B), electron hole reduced effective mass (mu), and one-electron band gap (E-g) 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 room temperature EA response in CH3NH3PbI3 follows the low-field Franz-Keldysh-Aspnes (FKA) effect. Following FKA analysis we find that mu = 0.12 +/- 0.03m(0), E-B = 7.4 meV, and E-g = 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.