Kastl Christoph, Schwartzberg Adam M, Maserati Lorenzo
Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Walter Schottky Institute and Physics Department, Technical University of Munich, Garching 85748, Germany.
ACS Nano. 2022 Mar 22;16(3):3715-3722. doi: 10.1021/acsnano.1c07281. Epub 2022 Feb 15.
Metal-organic species can be designed to self-assemble in large-scale, atomically defined, supramolecular architectures. A particular example is hybrid quantum wells, where inorganic two-dimensional (2D) planes are separated by organic ligands. The ligands effectively form an intralayer confinement for charge carriers resulting in a 2D electronic structure, even in multilayered assemblies. Air-stable layered transition metal organic chalcogenides 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, interexciton relaxation, and self-trapping of excitons within a few picoseconds (ps). The ps-decay provided by the self-trapping mechanism may be leveraged to unlock the material's potential for ultrafast optoelectronic applications.
金属有机物种可以被设计成大规模自组装，形成原子级定义的超分子结构。一个特别的例子是混合量子阱，其中无机二维（2D）平面由有机配体分隔。这些配体有效地为电荷载流子形成层内限制，从而产生二维电子结构，即使在多层组装中也是如此。最近发现，空气稳定的层状过渡金属有机硫族化合物在体相中容纳具有强光各向异性的紧密结合的二维激子。在这里，我们通过低温瞬态吸收光谱研究了典型金属有机硫族化合物[AgSePh]中的激发载流子动力学，解开了三种激子共振。我们的分析表明，存在一个复杂的弛豫级联过程，包括超快屏蔽和重整化、激子间弛豫以及激子在几皮秒（ps）内的自陷。自陷机制提供的皮秒级衰减可用于挖掘该材料在超快光电子应用方面的潜力。
