Enhancing Organic Semiconductor–Surface Plasmon Polariton Coupling with Molecular Orientation

Due to strong electric field enhancements, surface plasmon polaritons (SPPs) are capable of drastically increasing light-molecule coupling in organic optoelectronic devices. The electric field enhancement, however, is anisotropic, offering maximal functional benefits if molecules are oriented perpen...

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Bibliographic Details
Published in:	Nano letters Vol. 17; no. 10; pp. 6151 - 6156
Main Authors:	Brown, Steven J, DeCrescent, Ryan A, Nakazono, David M, Willenson, Samuel H, Ran, Niva A, Liu, Xiaofeng, Bazan, Guillermo C, Nguyen, Thuc-Quyen, Schuller, Jon A
Format:	Journal Article
Language:	English
Published:	United States American Chemical Society 11-10-2017
Subjects:	Molecular antennae photoluminescence reflectometry surface plasmon polaritons
Online Access:	Get full text
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Summary:	Due to strong electric field enhancements, surface plasmon polaritons (SPPs) are capable of drastically increasing light-molecule coupling in organic optoelectronic devices. The electric field enhancement, however, is anisotropic, offering maximal functional benefits if molecules are oriented perpendicular to the interface. To provide a clear demonstration of this orientation dependence, we study SPP dispersion and SPP-mediated photoluminescence at a model Au/small-molecule interface where identical molecules can be deposited with two very different molecular backbone orientations depending on processing conditions. First, we demonstrate that thin films of p-SIDT(FBTTh2)2 can be deposited with either all “in-plane” (parallel to substrate) or a 50/50 mix of in-plane/“out-of-plane” (perpendicular to substrate) optical transition dipoles by the absence or presence, respectively, of diiodooctane during spin-coating. In contrast to typical orientation control observed in organic thin films, for this particular molecule, this corresponds to films with conjugated backbones purely in-plane, or with a 50/50 mix of in-plane/out-of-plane backbones. Then, using momentum-resolved reflectometry and momentum-resolved photoluminescence, we study and quantify changes in SPP dispersion and photoluminescence intensity arising solely from changes in molecular orientation. We demonstrate increased SPP momentum and a 2-fold enhancement in photoluminescence for systems with out-of-plane oriented transition dipoles. These results agree well with theory and have direct implications for the design and analysis of organic optoelectronic devices.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1530-6984 1530-6992
DOI:	10.1021/acs.nanolett.7b02767