Effect of molecular and electronic structure on the light harvesting properties of dye sensitizers

TL;DR

This study investigates how molecular and electronic structures of PDI dye molecules influence their light absorption, using DFT and TDDFT calculations, to identify potential sensitizers for solar energy applications.

Contribution

It provides a systematic analysis of how halogen substitution affects the electronic and light-harvesting properties of PDI dyes, offering insights for designing better solar cell sensitizers.

Findings

Halogen atoms alter molecular geometry and electronic behavior.

Carboxylic acid groups do not significantly change the HOMO-LUMO gap.

Fluorinated, chlorinated, brominated, and iodinated PDIs are promising for solar applications.

Abstract

The systematic trends in structural and electronic properties of perylene diimide (PDI) derived dye molecules have been investigated by DFT calculations based on projector augmented wave (PAW) method including gradient corrected exchange-correlation effects. TDDFT calculations have been performed to study the visible absorbance activity of these complexes. The effect of different ligands and halogen atoms attached to PDI were studied to characterize the light harvesting properties. The atomic size and electronegativity of the halogen were observed to alter the relaxed molecular geometries which in turn influenced the electronic behavior of the dye molecules. Ground state molecular structure of isolated dye molecules studied in this work depends on both the halogen atom and the carboxylic acid groups. DFT calculations revealed that the carboxylic acid ligands did not play an important role in changing the HOMO-LUMO gap of the sensitizer. However, they serve as anchor between the PDI and substrate titania surface of the solar cell or photocatalyst. A commercially available dye-sensitizer, ruthenium bipyridine (RuBpy), was also studied for electronic and structural properties in order to make a comparison with PDI derivatives for light harvesting properties. Results of this work suggest that fluorinated, chlorinated, brominated, and iyodinated PDI compounds can be useful as sensitizers in solar cells and in artificial photosynthesis.