Electronic and Excitonic Structures of Inorganic–Organic Perovskite-Type Quantum-Well Crystal (C4H9NH3)2PbBr4

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Abstract
The electronic and excitonic structures of an inorganic–organic perovskite-type quantum-well crystal (C4H9NH3)2PbBr4 have been investigated by optical absorption, photoluminescence, electroabsorption, two-photon absorption, and magnetoabsorption spectroscopies. Excitons in (C4H9NH3)2PbBr4 are of the Wannier-type, and ns (n≥2) excitons form an ideal two-dimensional Wannier exciton system. The binding energy, longitudinal–transverse splitting energy, and exchange energy of 1s excitons have been determined to be 480, 70 and 31 meV, respectively. These high values originate from both a strong two-dimensional confinement and the image charge effect. These values are larger than those in (C6H13NH3)2PbI4, owing to the smaller dielectric constant of the well layer in (C4H9NH3)2PbBr4 than that in (C6H13NH3)2PbI4. The seemingly unusual electric-field dependence of excitons resonance is also reasonably understood by taking the image charge effect into account.