Theoretical research on the dye molecules with different π-bridge structures

Area of Science:

• Materials Science
• Photovoltaics
• Computational Chemistry

Background:

• Dye-sensitized solar cells (DSSCs) research surged after 1991, with organic dyes gaining traction due to lower costs and easier synthesis.
• Organic dyes offer a cost-effective, metal-free alternative with tunable structures and high photoelectric conversion efficiency.

Purpose of the Study:

• To investigate the structure-property relationships of organic dye molecules for enhanced solar cell performance.
• To design and evaluate novel π-bridge structures for improved light absorption and charge transfer properties.

Main Methods:

• Density Functional Theory (DFT) calculations using B3LYP/6-31G(d,p) for ground and excited state optimizations.
• Time-Dependent DFT (TD-DFT) with MPWPW91/6-31+G(d) to compute excitation energies and absorption spectra.

Main Results:

• Molecular modifications with rigid fused π-bridges, incorporating electron-rich and deficient segments, were explored.
• The designed π-bridges (dithienopyrrolobenzothiadiazole and dipyrrolo-dithienobenzothiadiazole) significantly redshifted absorption maxima.
• These modifications extended the excited-state lifetime and reduced the highest occupied molecule orbital (HOMO)-lowest unoccupied molecule orbital (LUMO) energy gap.

Conclusions:

• The developed π-bridge structures are effective in enhancing key photophysical properties of organic dyes.
• These findings provide a theoretical foundation for synthesizing more efficient organic dyes for dye-sensitized solar cells.