Document Type

Conference Paper

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This item is available under a Creative Commons License for non-commercial use only

Publication Details

In OptoIreland 2005. SPIE vol. 5826 (253), 2005. DOI:10.1117/12.603380 Available at http://spiedigitallibrary.aip.org/vsearch/servlet/VerityServlet?KEY=PSISDG&smode=strresults&sort=rel&maxdisp=25&threshold=0&pjournals=PSISDG&possible1=Lynch&possible1zone=author&fromvolume=5826&tovolume=5826&fromissue=1&toissue=1&OUTLOG=NO&deliveryType=spiedl&viewabs=PSISDG&key=DISPLAY&docID=3&page=1&chapter=0

Abstract

A series of π conjugated systems were studied by absorption, photoluminescence and vibrational spectroscopy. As is common for these systems, a linear relationship between the positioning of the absorption and photoluminescence maxima plotted against inverse conjugation length is observed. The relationships are in good agreement with the simple particle in a box method, one of the earliest descriptions of the properties of one-dimensional organic molecules. In addition to the electronic transition energies, it was observed that the Stokes shift also exhibited a well-defined relationship with increasing conjugation length, implying a correlation between the electron-vibrational coupling and chain length. This correlation is further examined using Raman spectroscopy, whereby the integrated Raman scattering is seen to behave superlinearly with chain length. There is a clear indication that the vibrational activity and thus nonradiative decay processes are controllable through molecular structure. The correlations between the Stokes energies and the vibrational structure are also observed in a selection of PPV based polymers and a clear trend of increasing luminescence efficiency with decreasing vibrational activity and Stokes shift is observable. The implications of such structure property relationships in terms of materials design are discussed.

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