Theoretical description of efficiency enhancement in DSSCs sensitized by newly synthesized heteroleptic Ru complexes

Abstract

Recently, some new series of heteroleptic ruthenium-based dyes, the so-called RD dyes, were designed and synthesized showing better performances compared to the well-known homoleptic N719. In this work, using the density-functional theory and its time-dependent extension, we have investigated the electronic structure and absorption spectra of these newly synthesized dyes, and compared the results to those of N3 dye to describe the variations of the properties due to the molecular engineering of the ancillary ligand. We have shown that the calculation results of the absorption spectra for these dyes using the PBE0 for the exchange-correlation functional are in better agreement with the experiment than using B3LYP or range-separated CAM-B3LYP. We have also derived a formula based on the DFT and used it to visually describe the level shifts in a solvent. The higher Jsc observed in these new dyes is explained by the fact that here, in contrast to N3, the excitation charge was effectively transferred to the anchoring ligand. Furthermore, we have shown that the difference dipole moment vectors of the ground and excited states can be used to determine the charge-transfer direction in an excitation process. Finally, different electron lifetimes observed in these dyes are explained by investigating the adsorption geometries and the relative orientations of iodine molecules in different "dyeI2" complexes.

A Synergetic Experimental and Computational Approach Towards a Better Comprehension of Redox Reactions of N3 Dye [cis‐bis(Isothiocyanato)‐Ruthenium(II)‐bis(2, 2’‐Bipyridine‐4,4’‐Dicarboxylic Acid] in Solution

“…Different functionals predict different absorption spectra with some of them reproducing more accurately the experimental one. We have studied this aspect in detail, finding that for Ru(II) complexes PBE0 gives the closest values to experimental results, in agreement with what has been reported in similar TDDFT studies . Figure shows the predicted and measured spectra for the N3 ; calculated results show the presence of the two lowest energy signals fairly close to the measured ones.…”

“…We 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 have studied this aspect in detail, finding that for Ru(II) complexes PBE0 [13] gives the closest values to experimental results, in agreement with what has been reported in similar TDDFT studies. [14] Figure 3 shows the predicted and measured spectra for the N3; calculated results show the presence of the two lowest energy signals fairly close to the measured ones. The first one corresponds to a pair of excitations with a small oscillator strength that is exhibited in a shoulder at 650 nm, composed mainly of two transitions: HOMO to LUMO and HOMO to LUMO + 1, as shown in molecular orbitals ( Figure 5a).…”

Low energy optical excitations as an indicator of structural changes initiated at the termini of amyloid proteins

“…The spatial distance between the barycenter of positive (∆ρ + (r)) and negative (∆ρ − (r)) regions can be used to quantify the charge transfer character of each excitation [34]. In addition, we also studied the dipole moment difference between the ground and excited states: [35] ∆µ = rρ exc dr − rρ gs dr…”

Theoretical Investigation of Iridium Complex with Aggregation-Induced Emission Properties

“…The PBE0 functional is often used in calculations for transition metal complexes, including iridium complexes, and has been shown to accurately reproduce the electronic spectra and geometry of such compounds [52][53][54][55][56][57][58]. The def2-TZVP, (8s7p6d1f)/[6s4p3d1f], basis set with the appropriate ECP was used for iridium, while for carbon, nitrogen, and oxygen, the TZVP basis, (11s6p1d)/[5s3p1d] and (5s1p)/[3s1p], for hydrogen was used [59,60].…”