Relationships for electron-vibrational coupling in conjugated Pi organic systems

L. O'Neill; P. Lynch; M. McNamara; H. J. Byrne

doi:10.1117/12.603380

3 June 2005 Relationships for electron-vibrational coupling in conjugated π organic systems

L. O'Neill, P. Lynch, M. McNamara, H. J. Byrne

Proceedings Volume 5826, Opto-Ireland 2005: Optical Sensing and Spectroscopy; (2005) https://doi.org/10.1117/12.603380
Event: OPTO-Ireland, 2005, Dublin, Ireland

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.

Citation Download Citation

L. O'Neill, P. Lynch, M. McNamara, and H. J. Byrne "Relationships for electron-vibrational coupling in conjugated π organic systems", Proc. SPIE 5826, Opto-Ireland 2005: Optical Sensing and Spectroscopy, (3 June 2005); https://doi.org/10.1117/12.603380

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