Exciton self-trapping causes picoseconds recombination in metal-organic chalcogenides hybrid quantum wells

TL;DR

This paper investigates the ultrafast exciton dynamics in metal-organic chalcogenide hybrid quantum wells, revealing that exciton self-trapping occurs within a few picoseconds and impacts potential optoelectronic applications.

Contribution

It provides the first detailed analysis of exciton relaxation processes, including self-trapping, in metal-organic hybrid quantum wells using transient absorption spectroscopy.

Findings

Exciton self-trapping occurs within a few picoseconds.

Multiple excitonic resonances are disentangled at low temperature.

Self-trapping mechanism may enable ultrafast optoelectronic devices.

Abstract

Metal-organic species can be designed to self-assemble in large-scale, atomically defined, supramolecular architectures. Hybrid quantum wells, where inorganic two-dimensional (2D) planes are separated by organic ligands, are a particular example. The ligands effectively provide an intralayer confinement for charge carriers resulting in a 2D electronic structure, even in multilayered assemblies. Air-stable metal organic chalcogenides hybrid quantum wells have recently been found to host tightly bound 2D excitons with strong optical anisotropy in a bulk matrix. Here, we investigate the excited carrier dynamics in the prototypical metal organic chalcogenide [AgSePh], disentangling three excitonic resonances by low temperature transient absorption spectroscopy. Our analysis suggests a complex relaxation cascade comprising ultrafast screening and renormalization, inter-exciton relaxation, and self-trapping of excitons within few picoseconds. The ps-decay provided by the self-trapping mechanism may be leveraged to unlock the material's potential for ultrafast optoelectronic applications.