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Strong Tunable Visible Absorption Predicted for Polysilo-acenes Using TDDFT Calculations

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journal contribution
posted on 17.12.2015, 09:29 by K. L. Dimuthu M. Weerawardene, Christine M. Aikens
The optical properties of polysilo-acenes with two to six fused rings are studied using time-dependent density functional theory. We show that there are three spectral features in the absorption spectra analogous to α, β, and p-band peaks known for carbon-based acenes. The β peak is the most prominent feature in each spectrum, which appears in the visible region. Both α and β peaks originate due to identical transitions that are polarized along the long axis of the system. The constructive interaction of quasi-degenerate configurations gives rise to the strong β peak, while their destructive interaction results in the α peak with a low oscillator strength. Because the constructive interaction of configurations is characteristic of plasmons in acenes and noble metal nanoparticles, the β peak can be identified as plasmonic for polysilo-acenes. The strong visible absorption and the potential for use in existing Si-technology affirm the interest in polysilo-acenes.