Computational Study on D-π-A-Based Electron Donating and Withdrawing Effect of Metal-Free Organic Dye Sensitizers for Efficient Dye-Sensitized Solar Cells

A new generation of metal-free organic dyes with a range of donor (D1) and acceptors (A1-A3) were designed and examined for dye-sensitized solar cells (DSSCs) based on (3a) dye as a literature. Triphenylamine (TPA), thiophene (pi) and 2-cyanoacrylic acid groups each perform the roles of an acceptor (A), donor (D) and spacer in order to produce a D-pi-A system. To investigate the intramolecular charge transfer (ICT), electronic distribution, ultra-violet visible (UV-Vis) absorption wavelengths, molecular electrostatic potential (MEP) and photovoltaic (PV) parameters of the D1 and A1-A3 molecules, density functional theory (DFT) and time-dependent DFT (TD-DFT) were used. The classification of the tunable donor D1 and A1-A3 determines the PV performance of the dye molecules. Results show that the A2 dye replacement group increases the performance of PV cells via red-shifting absorption spectra. Also, when compared to 3a, A2 dye have lower energy gap (E-g) and superior UV-Vis spectra that cover the full visible range. These results demonstrate the viability of molecular tailoring as an approach to improve D-pi-A sensitizer proposal for efficient DSSCs fabrication.