Theoretical exploration of 1,3-Indanedione as electron acceptor-cum-anchoring group for designing sensitizers towards DSSC applications

The present work highlights the DFT and TD-DFT calculations of a few organic sensitizers designed based on a new electron-acceptor, 1,3-indanedione, which is a well-known electron-acceptor for designing new electron donor-acceptor molecules. Nine organic sensitizers (GR1-9) have been designed based on a modified 1,3-indanedione electron-acceptor and conventional electron-donor moieties. Optimization studies reveal that all dyes have twisted configurations, and therefore, the aggregation on the TiO2 semiconductor is expected to be less. GR2 dye shows the smallest energy gap, 2.43 eV, as compared to others which indicates an effective electronic excitation and injection. The dyes' energy levels are compatible with the conduction band of TiO2 and redox potentials of the redox couple. Thermodynamic parameters indicate that the GR1, GR2, and GR5 dyes regenerate at a faster rate as compared to the other dyes. Further, NBO calculations demonstrate the dipolar nature of the designed molecules. Electronic spectra of dyes were red-shifted by 18-29 nm in acetonitrile solvent, which shifts further towards red-region upon adsorbing on to titania. The absorption spectrum of the GR1@TiO2 system shows a remarkable shift, 92 nm, and extends to the NIR region. The electron density of LUMO and LUMO + 1 is majorly confined to TiO2 moiety upon binding, which indicates complete electron donation from dye to the TiO2. Overall, our studies reveal that the 1,3-indanedione skeleton has the potential to serve as an electron-acceptor in designing new organic sensitizers for DSSCs. Therefore by conjugating conventional electron-donors with the 1,3-indanedione electron-acceptor, a new class of organic sensitizers can perhaps be synthesized for DSSC applications.

Automated summary

The present work focuses on the DFT and TD-DFT calculations of organic sensitizers designed based on a new electron-acceptor, 1,3-indanedione. Nine organic sensitizers have been designed and optimized, revealing twisted configurations and expected low aggregation on TiO2. GR2 dye shows the smallest energy gap, indicating effective electronic excitation and injection. Thermodynamic parameters suggest faster regeneration for GR1, GR2, and GR5 dyes. NBO calculations demonstrate the dipolar nature of the designed molecules. The absorption spectra of dyes show red-shifts in acetonitrile solvent and further red-shifts upon adsorbing on to titania.