First principle investigation of new metal-free organic dye molecular for DSSCs: effects of π-conjugated groups

Based on 1-phenylpyrrolidine (PT) dye, six new metal-free organic molecules S1-S6, containing PT as donor (D) connected through different linkages (pi) and cyanoacrylic acid as acceptor (A), were designed and studied for dye sensitised solar cells (DSSCs). In this paper, D-pi-A system of S1-S6 dye molecules was investigated by quantum chemical calculations to inspect the optical absorption properties and photovoltaic (PV) parameters. In particular, there are applied three long-range corrected (LC) functionals, such as B3PW91, CAM-B3LYP and omega B97XD with the time-dependent DFT (TD-DFT) calculation to systematically investigate the absorption peak in PT dye. From the calculated results, CAM-B3LYP functional was a good match with the PT dye. Therefore, the S1-S6 molecules' optical absorption spectra have been computed by using the CAM-B3LYP/6-31+G(d) theory. The conductor-like polarisable continuum model (C-PCM) results show that the precise absorption spectra have attained solvent effect included in the excited state geometries. The frontier molecular orbitals (FMOs) of the HOMOs and LUMOs energies of S1-S6 derivatives confirm positive results on the dye regeneration and electron injection processes. The outcomes display that the benzo[c][1,2,5]thiadizole (S4) and benzo[c][1,2,5]oxadizole (S5) molecules are the most suitable spacers for D to A, owing to longer absorption peaks and revealing red-shifted optical absorption.

Automated summary

In this study, six new metal-free organic molecules were designed for dye sensitised solar cells and investigated for their optical absorption properties and photovoltaic parameters. The CAM-B3LYP functional was found to be a good match for the PT dye. The molecules containing benzo[c][1,2,5]thiadizole (S4) and benzo[c][1,2,5]oxadizole (S5) were identified as the most suitable spacers for D to A due to their longer absorption peaks and red-shifted optical absorption.