Evolution of the Nature of Excitons and Electronic Couplings in Hybrid 2D Perovskites as a Function of Organic Cation π‐Conjugation

Abstract

2D perovskites have attracted much attention, due to their organic–inorganic hybrid nature and layered configuration. Multi-quantum-well structures then generally form since the inorganic frameworks and organic spacers have typically well-separated frontier energy levels. Here, it is focused on the opposite picture where wavefunction hybridization occurs between the frontier orbitals of the two components. Such a hybridization emerges upon tuning the strength of electronic coupling between the inorganic and organic layers. A series of model diammonium organic spacers is theoretically designed with varying extent of π-conjugation along their backbones. Wavefunction hybridization is realized in a Dion-Jacobson 2D perovskite combining PbI4 inorganic layers with anthracene-bis(ethan-1-ammonium) organic spacers. An analysis of the electronic band structures points to electronic couplings as high as 30–40 meV between the organic and inorganic components. Such couplings can lead to the formation of interfacial hybrid excitons or to the appearance of Dexter-type energy transfer conducive to phosphorescence in the organic layers. Overall, the results highlight that a variety of excitonic behaviors could be observed by tuning the degree of conjugation of the organic cations and the structural proximity and electronic couplings between the organic and inorganic constituents.