Optical Absorption and Photoluminescence Properties of Pb(I, Br)-Based Two-Dimensional Layered Perovskite

Abstract

The influence of ( C 6 H 5 C 2 H 4 NH 3 ) 2 Pb(Br x I 4- x ) concentration on the formation of mixed crystals and optical properties of these materials was investigated. Thin films of microcrystalline ( C 6 H 5 C 2 H 4 NH 3 ) 2 Pb(Br x I 4- x ) were prepared by the spin-coating method using different concentrations of DMF solutions. Macroscopic inhomogeneity of the composition due to the precipitation of undesired phases could be suppressed by controlling the ( C 6 H 5 C 2 H 4 NH 3 ) 2 Pb(Br x I 4- x ) concentration. These films showed strong exciton absorption with large (250–430 meV) binding energy due to both the quantum and dielectric confinement effect. Replacing I with Br made it possible to shift the exciton band to the blue region; however, photoluminescence from the mixed crystals gradually broadened with increasing the Br content.