  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.
