Miwa Kuniyuki, Imada Hiroshi, Imai-Imada Miyabi, Kimura Kensuke, Galperin Michael, Kim Yousoo
Surface and Interface Science Laboratory , RIKEN , Wako , Saitama 351-0198 , Japan.
Department of Chemistry and Biochemistry , University of California, San Diego , La Jolla , California 92093 , United States.
Nano Lett. 2019 May 8;19(5):2803-2811. doi: 10.1021/acs.nanolett.8b04484. Epub 2019 Feb 5.
Electron transport and optical properties of a single molecule in contact with conductive materials have attracted considerable attention because of their scientific importance and potential applications. With the recent progress in experimental techniques, especially by virtue of scanning tunneling microscope (STM)-induced light emission, where the tunneling current of the STM is used as an atomic-scale source for induction of light emission from a single molecule, it has become possible to investigate single-molecule properties at subnanometer spatial resolution. Despite extensive experimental studies, the microscopic mechanism of electronic excitation of a single molecule in STM-induced light emission has yet to be clarified. Here we present a formulation of single-molecule electroluminescence driven by electron transfer between a molecule and metal electrodes based on a many-body state representation of the molecule. The effects of intramolecular Coulomb interaction on conductance and luminescence spectra are investigated using the nonequilibrium Hubbard Green's function technique combined with first-principles calculations. We compare simulation results with experimental data and find that the intramolecular Coulomb interaction is crucial for reproducing recent experiments for a single phthalocyanine molecule. The developed theory provides a unified description of the electron transport and optical properties of a single molecule in contact with metal electrodes driven out of equilibrium, and thereby, it contributes to a microscopic understanding of optoelectronic conversion in single molecules on solid surfaces and in nanometer-scale junctions.
单个分子与导电材料接触时的电子输运和光学性质因其科学重要性和潜在应用而备受关注。随着实验技术的最新进展，特别是借助扫描隧道显微镜（STM）诱导发光，其中STM的隧穿电流被用作从单个分子诱导发光的原子尺度光源，已经能够在亚纳米空间分辨率下研究单分子性质。尽管进行了广泛的实验研究，但STM诱导发光中单个分子的电子激发微观机制仍有待阐明。在此，我们基于分子的多体状态表示，提出了一种由分子与金属电极之间的电子转移驱动的单分子电致发光的公式。使用非平衡哈伯德格林函数技术结合第一性原理计算，研究了分子内库仑相互作用对电导和发光光谱的影响。我们将模拟结果与实验数据进行比较，发现分子内库仑相互作用对于重现单个酞菁分子的最新实验至关重要。所发展的理论为非平衡状态下单个分子与金属电极接触时的电子输运和光学性质提供了统一描述，从而有助于从微观角度理解固体表面和纳米尺度结中单个分子的光电转换。
