外延对准有机-无机二维异质晶体中的双模激子耦合

中文摘要 AI 辅助

二维（2D）由分子与半导体组成的异质晶体可作为研究界面激子及未来光电应用的理想平台，但这些原子级尖锐界面上的能量与电荷流动仍不明确。本研究以PTCDA-MoS₂作为典型的二维有机-无机异质结构，揭示了组成晶体间的双模激子耦合：通过物理气相组装在单层MoS₂上生长单层分辨的PTCDA分子晶体，利用电子衍射确定其包括堆叠角在内的晶体学细节；异质结构形成后，PTCDA的光致发光因有机到无机的空穴转移完全猝灭，而MoS₂的光致发光随PTCDA厚度显著增强；通过差分反射与光致发光激发光谱发现，该增强源于两种不同机制：基态电荷转移向MoS₂注入空穴，抑制负三激子形成并增强中性激子的辐射复合；此外，PTCDA与MoS₂的光谱重叠实现了共振能量转移，将激发能从PTCDA转移至MoS₂；本研究调和了此前提出的机制，建立了电荷与能量转移协同调控有机-无机界面激子耦合的统一框架。

英文摘要

Two-dimensional (2D) heterocrystals comprising molecules and semiconductors can serve as an ideal platform for studying interfacial excitons and for future optoelectronic applications, yet the energy and charge flow across these atomically sharp interfaces remain unclear. In this work, we investigated PTCDA-MoS2 as a prototypical 2D organic-inorganic heterostructure and revealed dual-mode exciton coupling between the constituent crystals. Monolayer-resolved PTCDA molecular crystals were grown on monolayer MoS2 via physical vapor assembly, and their crystallographic details, including the stacking angle, were determined by electron diffraction. Upon the formation of the heterostructures, PTCDA's photoluminescence was completely quenched because of organic-to-inorganic hole transfer, whereas that of MoS2 increased markedly with PTCDA thickness. Using differential reflectance and photoluminescence excitation spectroscopy, we found that the enhancement arises from two distinct mechanisms. Ground-state charge transfer injects holes into MoS2, which suppresses negative trion formation and enhances the radiative recombination of neutral excitons. In addition, resonant energy transfer, enabled by spectral overlap between PTCDA and MoS2, diverts excitation energy from PTCDA to MoS2. Our findings reconcile previously proposed mechanisms and establish a unified framework in which charge and energy transfer cooperate to govern exciton coupling at organic-inorganic interfaces.

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23 pages, 5 figures