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Chen G, Luo Y, Gao H, Jiang J, Yu Y, Zhang L, Zhang Y, Li X, Zhang Z, Dong Z. Spin-Triplet-Mediated Up-Conversion and Crossover Behavior in Single-Molecule Electroluminescence. PHYSICAL REVIEW LETTERS 2019; 122:177401. [PMID: 31107062 DOI: 10.1103/physrevlett.122.177401] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Revised: 02/22/2019] [Indexed: 05/24/2023]
Abstract
Scanning-tunneling-microscope-induced light emission serves as a powerful approach in revealing and manipulating the optical properties of molecular species, intermolecular energy transfer, and plasmon-molecule coupling. Earlier studies have established the existence of molecular up-conversion electroluminescence in diverse situations, but the underlying microscopic mechanisms are still under active debate, dominated by intermolecular triplet-triplet annihilation and plasmonic pumping. Here we report on the experimental realization of up-conversion electroluminescence from a prototypical single phthalocyanine molecule, allowing us to unambiguously rule out mechanisms based on intermolecular coupling and also offering unprecedented opportunities to elucidate much richer characteristics unforeseen in previous studies. In particular, the bias-dependent emission intensity displays three distinct regions with different nonlinear current dependences, which can be attributed to crossover behavior caused by the interplay between inelastic electron scattering and carrier-injection processes. We also develop a microscopic description to capture the essential physics involved in up-conversion electroluminescence mediated by a proper intermediate spin-triplet state.
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Affiliation(s)
- Gong Chen
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
- School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan 450052, China
| | - Yang Luo
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Hongying Gao
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jun Jiang
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yunjie Yu
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Li Zhang
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yang Zhang
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xiaoguang Li
- Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China
| | - Zhenyu Zhang
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Zhenchao Dong
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
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