Absorption spectra of natural pigments as sensitizers in solar cells by TD-DFT and MRPT2: protonated cyanidin

Abstract

The study of molecular species suitable as sensitizers in solar cells involves the understanding of their visible absorption spectrum. In this article we present a detailed theoretical study of the visible band which has been observed for cyanidin in acid solution. We performed accurate DFT and MRPT2 calculations on the protonated cyanidin in vacuo and in solution, where we have also computed the lineshape profile by including the effects of nuclear degrees of freedom in the harmonic approximation.

Unraveling the molecular mechanisms of color expression in anthocyanins

“…3,6 This variability and complexity of color expression makes the industrial utilization of anthocyanins a challenging endeavor, compared to synthetic dyes which are more stable and predictable. Thus a deep understanding of the mechanisms of color expression in these molecules is still needed, in spite of recent extensive experimental 2,3,5,7,8 and theoretical [9][10][11][12][13][14][15][16] efforts. Moreover, most of the available studies concern the cationic species-responsible for the red hues only-while only few studies have focused so far on the neutral and negative species, which are of striking interest for industrial applications.…”

“…Predicting the color using theory and computational methods, however, is not as straightforward. 17,18 Efforts in this direction have comprised quantum chemical calculations performed at various levels of theory, ranging from semiempirical methods, [13][14][15]19 to post Hartree-Fock 12 and TDDFT, 9,10,16 most of which, however, focused on the cation form only, and did not address charge, tautomerism, and conformation effects, which are expected to be important. Furthermore, the absorption spectrum and perceived color of a solution depend on the different out-of-equilibrium molecular geometries that are experienced by thermal fluctuations, as well as on the interaction with the solvent.…”

Disentangling vibronic and solvent broadening effects in the absorption spectra of coumarin derivatives for dye sensitized solar cells

“…However this has been mostly done by computing the excitation energies of candidate dyes [16][17][18] while only a few computational works have addressed the role of vibronic contributions. 19,20 Their inclusion is actually necessary to get a direct comparison with the experimental spectral lineshapes, since vibronic transitions affect both the spectral maximum and width and eventually determine the "color" of the dyes. 21,22 In a system as complex as DSSC the absorption lineshape depends not only on vibronic effects, but also on the solvent, the adsorption on the semiconductor and possible dyes aggregations.…”

“…However this has been mostly done by computing the excitation energies of candidate dyes [16][17][18] while only a few computational studies have addressed the role of vibronic contributions. 19,20 Their inclusion is actually necessary to get a CNR-Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), UOS di Pisa, Area della Ricerca, via G. Moruzzi 1, I-56124 Pisa, Italy. E-mail: fabrizio.santoro@iccom.cnr.it b Physical Chemistry, Faculty of Science, University of Ma ´laga, Ma ´laga, 29071, Spain † Electronic supplementary information (ESI) available: Comparison of VH spectra and AH spectra computed either in Cartesian or in internal coordinates and comparison of TD and TI spectra for C343 at 0 K; plots of the HOMO and the LUMO for different chromophores; relative stability of the protomers of C343; further analysis of the CT character and its effect on FC factors; for nkx-2753 further comparisons of CAM-B3LYP and PBE0 spectra in the gas-phase and in ethanol.…”

Comparison of several protocols for the computational prediction of the maximum absorption wavelength of chrysanthemin

“…In this study, two different protocols obtained from the combination of the two mentioned above were evaluated and compared with the original protocols in their ability to calculate the spectrum of chrysanthemin. The results have been compared with the available experimental data [24,25]. The good agreement of one of these methods with the available experimental data indicates that it can be used with confidence in future studies of anthocyanin-related pigments of potential interest for DSSC.…”