Theoretical study of photon emission from molecular wires

Abstract

We explore theoretically the principles that govern photon emission from single-molecule conductors carrying electric currents between metallic contacts. The molecule and contacts are represented by a generic tight-binding model. The electric current is calculated using Landauer theory and the photon emission rate is obtained using Fermi's golden rule. The bias-dependence of the electronic structure of the molecular wire is included in the theory in a simple way. Conditions under which significant photon emission should occur are identified and photon spectra are calculated. We predict the photon emission rate to be more sensitive than the electric current to coupling asymmetries between the molecule and contacts. This has important implications for the design and interpretation of STM experiments searching for electroluminescence from individual molecules. We discuss how electroluminescence may be used to measure important characteristics of the electronic structure of molecular wires such as the HOMO-LUMO gap and location of the Fermi level of the contacts relative to the HOMO and LUMO. The feasibility of observing photon emission from Au/benzene-dithiolate molecular wires is also discussed.

Physical Review B, in press

References in corpus (6)

• ab initio modeling of open systems: charge transfer, electron conduction, and molecular switching of a C_{60} device
• Theoretical Study of Electrical Conduction Through a Molecule Connected to Metallic Nanocontacts
• Molecular Spintronics: Spin-Dependent Electron Transport in Molecular Wires
• Current-Driven Conformational Changes, Charging and Negative Differential Resistance in Molecular Wires
• Multi-terminal Molecular Wire Systems: A Self-consistent Theory and Computer Simulations of Charging and Transport
• State Orthogonalization by Building a Hilbert Space: A New Approach to Electronic Quantum Transport in Molecular Wires

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• Modeling elastic and photoassisted transport in organic molecular wires: length dependence and current-voltage characteristics
• Linear optical response of current-carrying molecular junction: A NEGF-TDDFT approach
• Role of electronic structure in photoassisted transport through atomic-sized contacts
• Electroluminescence spectra in weakly coupled single-molecule junctions
• Understanding the electroluminescence emitted by single molecules in scanning tunneling microscopy experiments
• Two-probe theory of scanning tunneling microscopy of single molecules: Zn(II)-etioporphyrin on alumina