Proceedings of International Conference on Perovskite Thin Film Photovoltaics and Perovskite Photonics and Optoelectronics (NIPHO24)
Publication date: 25th April 2024
Hybrid organic–inorganic perovskites (HOIPs) have emerged as excellent materials for solar cell applications. Indeed, their extreme tunability and facile synthesis have opened the door to many new applications. Chiral HOIPs are attracting great interest as promising frameworks for chiroptoelectronics as well as spintronics applications. The chiroptical properties observed in chiral HOIPs can be explained understanding the chirality transfer from the chiral organic molecules to the achiral inorganic octahedra. A key element of the chirality transfer mechanism involves the distortion of the coordination geometry of the inorganic octahedra induced by the presence of chiral ligands. The specific process through which a chiral bias is generated from a chiral organic ligand to the inorganic scaffold has remained unclear until now.[1,2] In this study, we propose a tailored simulation workflow based on Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT)[3] to theoretically explore the chirality transfer mechanism inducing chirality generation and coordination geometry distortion. To this aim, we investigate the chiroptical response of lead- and tin-based 2D chiral perovskites, specifically 2D R- and S-(MBA+)2PbI4[4] and R- and S-(MBA+)2SnI4.[5] We explore the most impactful factors influencing their Circular Dichroism (CD) signals through ab-initio molecular dynamics simulations and the analysis of the density of electronic states (DOSs). Our findings reveal that the relevant chiroptical features are linked to a chirality transfer event driven by a metal–ligand overlap of electronic levels. This effect is more evident for tin-based chiral perovskites showing higher excitonic coupling. Recent simulations on thermodynamics and kinetics aspects of the early stage of their chiral formation will be also discussed.