Novel triphenylamine-based porphyrins: Synthesis, structural characterization, and theoretical investigation for dye-sensitized solar cell applications

Abstract

In this work, we have synthesized a series of novel porphyrin derivatives, 8, 12, and 16 in high yields. The new porphyrin derivatives are equipped with different aromatic substituents at the peripheral position. The structures of the new compounds were confirmed by elemental and spectral analyses. Among these porphyrin structures, porphyrins 8, 12, and 16 were molecularly designed and synthesized based on triphenylamine (TPA), as the core donor (DTPA), linked to one, two, or three porphyrin (DPorph) moieties with different numbers of anchoring groups (AG) to generate: DTPA-π-DPorph-A(DE1), DTPA(π-DPorph-A)2(DE2) and DTPA(π-DPorph-A)3(DE3). The structural, electronic, and spectroscopic properties of the dyes have been obtained by using the density functional theory (DFT) and time-dependent-DFT calculations. Based on the DFT studies, porphyrins 8, 12, and 16 possess all thermodynamics requirements to be used for DSSCs as the HOMO values for these three porphyrins are greater than the electrolyte's redox potential (I−/I3−, -5.2 eV), while the LUMO level more negative than the conduction band of TiO2 (- 4.2 eV), which indicate that these structures are suitable as sensitizers in DSSCs. All proposed structures were estimated in the gaseous state based on their optimized ground state geometry to estimate their EHOMO, ELUMO, and HOMO-LUMO energy gaps. porphyrins 8, 12, and 16 electronic excitations were also probed using TD-DFT experiments, which were performed under the impact of time-dependent disturbances. The simulated absorption spectra of these structures revealed the porphyrins' typical Soret- and Q-bands. porphyrin 16 with tri-cyanoacrylic acid anchoring groups has a wider absorption spectrum than other porphyrins (8, 12), and their Soret- and Q-bands are red-shifted. As a final step, we analyzed and described the DSSC's performance using the concept of DFT reactivity indices. A more efficient DSSC can be built using this approach to correlate cell efficiency with molecular properties.