Assessment of time-dependent density functionals for the electronic excitation energies of organic dyes used in DSSCs

Abstract

The absorption spectra modeled as the vertical excitation energies of 13 dye sensitizers used in dye-sensitized solar cells (DSSCs) are benchmarked by means of time-dependent (TD)-DFT, using 36 functionals from...

Tuning the photophysical properties ofBODIPYdyes used inDSSCsas predicted by double‐hybridTD‐DFT: The role of the methyl substituents

“…Another point to consider is that the long alkyl chains at position 8 that are also typical in dye sensitizers are modeled with a simple methyl group in all dyes explored in the present work. This approximation will have no effect on the electronic structure and spectra of the BODIPY highly conjugated systems, and is a valid modeling strategy frequently used to reduce the computational cost of calculations [60, 61, 140–142]. Finally, we will only be interested in the effect of methyl groups in the present study, and we will not study the effect of the nature of the substituent on the spectra, since it was previously found by Mukherjee that electronic structure of BODIPY compound is only affected by the position and not by the nature of the substituent [46].…”

“…However, many previous studies demonstrated the validity of using the vertical approximation for BODIPY compounds [63, 77]. Therefore, all our ES results are performed according to the vertical excitation model [60, 61, 63, 73, 77, 144]. Furthermore, in an experimental photovoltaic solar cell device, the dye sensitizers together with the electrolyte redox couple are usually dissolved in an organic solvent.…”

“…Another point to consider is that the long alkyl chains at position 8 that are also typical in dye sensitizers are modeled with a simple methyl group in all dyes explored in the present work. This approximation will have no effect on the electronic structure and spectra of the BODIPY highly conjugated systems, and is a valid modeling strategy frequently used to reduce the computational cost of calculations [60,61,[140][141][142].…”

“…An accurate computational modeling of the dye chromophores, the basic building units of electrochemical DSSC devices, can greatly help the design of novel efficient dye sensitizers [34–37, 60, 61]. However, an accurate description of the electronic ESs of BODIPYs is a real challenge in computational chemistry, in spite of the numerous computational benchmark and theoretical modeling studies dedicated for such molecular systems [48, 60, 62–84].…”

“…In general, the MAE values of the double hybrid density functionals B2PLYP [88], DSD-BLYP [89,90], and DSD-PBEP86 [89,90] was found to be around 0.1 eV, while common hybrid and range separated hybrid functionals was found to produce average errors that are substantially higher than 0.3 eV [60]. Double hybrid (DH) density functionals includes a fraction of perturbative MP2 correlation part in the exchange-correlation (xc) functionals [88,91,92], and are therefore very promising in ES calculations via the TD-DFT regime [60,61,77,[93][94][95][96][97][98][99][100]. In the present work, we use the double hybrid B2PLYP functional to predict the electronic excited properties of 16 proposed BODIPY based dye sensitizer that have been designed according to the number and position of the methyl groups at the BODIPY moiety in a BODIPY based dye sensitizer with a push-pull, or D-π-A, architecture; see Figure 2.…”