Time dependent – density functional theory characterization of organic dyes for dye-sensitized solar cells

Abstract

We aim at providing better insight into the parameters that govern the intramolecular charge transfer (ICT) and photo-injection processes in dyes for dye-sensitised solar cells (DSSC). Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations are utilized to study the geometry, electronic structure, electrostatic potential (ESP) and absorption spectrum, for a representative donor-π bridge-acceptor (D–π–A) dye for DSSC. The coplanar geometry of the dye (D1) facilitates strong conjugation and considerable delocalization originating the π CT interaction from donor to acceptor orbitals and the hyper-conjugative interactions involving Rydberg states. A model simulating the adsorption of the dye on the TiO₂ surface is utilized to estimate binding energies. The effect of fluorine substituents in the π-spacer on the quantum efficiency of DSSCs was investigated. Gibb’s free energy values, redox potentials, excited state lifetime, non-linear optical properties (NLO) and driving forces for D1 and its fluorinated derivatives were computed.

Keywords:

• Dye-sensitised solar cells
• density functional theory
• D–π–A
• organic dyes
• absorption spectra

Acknowledgment

The authors acknowledge with thanks DSR support for Scientific Research. The computational work described in this paper was supported by King Abdulaziz University’s High Performance Computing Center (Aziz Supercomputer, http:/hpc.kau.edu.sa).