Optical Properties and Electronic Structures of Self-Organized Quantum Well (CnH2n+1NH3)2PbX4 (X=I, Br, Cl)

Abstract

We observed a prominent absorption peak due to the lowest exciton state in the two-dimensional perovskite crystals at 2.55eV for (C₁₀H₂₁NH₃)₂PbI₄, 3.17eV for (C₁₀H₂₁NH₃)₂PbBr₄, and 3.75eV for (C₁₀H₂₁NH₃)₂PbCl₄, respectively. The less prominent structures in the absorption spectrum above the lowest exciton shifts as a whole, as the halogen goes from I to Cl, which shows that the optical excitation in these compounds is not due to the intraatomic transition in the Pb atom (cationic transition) but due to the interatomic transition from the halogen atom to the Pb atom. We performed tight binding calculations of the electronic band structure, which explain the energy shift and the polarization dependence of the reflection spectra.