Enhanced photoluminescence from a molecular tunneling junction (Conference Presentation)

Alfred J. Meixner; Kai Braun; Xiao Wang; Dai Zhang

doi:10.1117/12.2274408

19 September 2017 Enhanced photoluminescence from a molecular tunneling junction (Conference Presentation)

Alfred J. Meixner, Kai Braun, Xiao Wang, Dai Zhang

Proceedings Volume 10362, Organic Light Emitting Materials and Devices XXI; 1036207 (2017) https://doi.org/10.1117/12.2274408
Event: SPIE Organic Photonics + Electronics, 2017, San Diego, California, United States

Abstract

We demonstrate enhanced photoluminescence (PL) from an optically pumped bias driven molecular tunneling junction (Au-substrate/self assembled molecular monolayer/Au-tip) with molecules chemically bound to the Au substrate. The gap between a sharp gold tip and a flat gold substrate covered with a self-assembled monolayer (SAM) of 5-chloro-2 mercaptobenzothiazole (Cl-MBT) molecules can be used as an extremely small optical gain medium. When a bias-voltage is applied between tip and sample such that electrons tunnel from the Cl-MBT’s highest occupied molecular orbital (HOMO) to the tip, holes are left behind in the molecules. These can be repopulated by hot electrons that are created by the laser-driven plasmon oscillation on the metal surfaces enclosing the molecule. Emission of photons occurs from the recombination of plasmon excited hot electrons with holes in the HOMO of surface bound molecules below the tip. Varying the laser pump power or alternatively the applied bias voltage shows in both cases a distinct threshold above which enhancement of the optical signal occurs. Solving the rate equations for this system shows that optical feed-back by the gap mode’s near field can efficiently stimulate the emission process. The system reflects many essential features of a superluminescent organic light emitting diode.

Conference Presentation

Citation Download Citation

Alfred J. Meixner, Kai Braun, Xiao Wang, and Dai Zhang "Enhanced photoluminescence from a molecular tunneling junction (Conference Presentation)", Proc. SPIE 10362, Organic Light Emitting Materials and Devices XXI, 1036207 (19 September 2017); https://doi.org/10.1117/12.2274408

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