Electro-Absorption Spectroscopy of Hybrid Organic-Inorganic Perovskites

The method of Electro Absorption (EA) related to the third-order nonlinear optical susceptibility allows probing electronic states of semiconductors better than linear absorption since it is a modulation technique. Using the EA spectroscopy in two-dimensional (2D)- and three-dimensional (3D)-hybrid organic-inorganic perovskites (HOIP) at various temperatures, we obtained the optical band gap, the 1s exciton energy, and the exciton binding energy (Eb) in these materials. We found that whereas Eb is of the order of 20 meV in 3D-HOIP, it is of the order of 250 meV in 2D-HOIP due to dielectric and dimensionality enhancement. We also found the signature of internal fields in some 2D-HOIP that indicates the existence of ferroelectricity in these compounds.