Exciton-band tuning induced by the width of the cation in 2D lead iodide perovskite hybrids

Abstract

It was previously demonstrated that the exciton energy of 2D hybrid organic–inorganic A₂PbI₄ perovskites is correlated with the Pb–I–Pb bond angle of the inorganic layer. We demonstrate that this angle can be tuned by changing the width of the cation and that the exciton band energy can be varied over ca. 100 meV, at least within a limited series of A₂PbI₄ compounds where A is a 2-(3,5-disubstitutedphenyl)ethylammonium or 2-(3-substitutedphenyl)ethylammonium ion and where the substituents are H, F, Cl, Br, or Me. Seven new crystal structures are presented here.