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

Area of Science:

• Materials Science
• Quantum Chemistry
• Optoelectronics

Background:

• Acenes are organic molecules with fused aromatic rings, known for their unique optical and electronic properties.
• Polysilo-acenes, silicon-containing analogs of acenes, are being explored for novel material applications.
• Understanding their optical properties is crucial for developing new optoelectronic devices.

Purpose of the Study:

• To investigate the optical absorption spectra of polysilo-acenes with varying numbers of fused rings (two to six).
• To identify and characterize spectral features analogous to known acene absorption bands (α, β, and p-bands).
• To determine the origin and nature of these spectral features, particularly the prominent β peak.

Main Methods:

• Utilizing time-dependent density functional theory (TD-DFT) to calculate optical properties.
• Analyzing absorption spectra to identify key spectral features and their intensities.
• Investigating electronic transitions and their polarization characteristics.

Main Results:

• Three main spectral features analogous to α, β, and p-bands were identified in polysilo-acene absorption spectra.
• The β peak is the most intense feature, located in the visible region, and arises from constructive interaction of quasi-degenerate configurations.
• Both α and β peaks originate from transitions polarized along the long axis; the β peak's intensity is attributed to constructive configuration interaction, indicative of plasmonic behavior.

Conclusions:

• The β peak in polysilo-acenes exhibits plasmonic characteristics, similar to those observed in carbon acenes and noble metal nanoparticles.
• Strong visible light absorption and compatibility with existing silicon technology make polysilo-acenes promising for optoelectronic applications.