A DFT and TDDFT Study of PCM Effect on N3 Dye Absorption in Ethanol Solution

Abstract

[Ru(H 2 dcbpy) 2 (SCN) 2 ], known as N3 dye, one of the best sensitizer for DSSC, was the focus of this research. All calculations were carried out with Gaussian03, using B3LYP hybrid functional DFT and TDDFT for ground state geometry optimization and excited states calculations respectively. Basis setused in all calculations was 3-21G* for all elements. Polarized Continuum Model was used for modelling the complex in ethanol solution. Combination of 3-21G* basis set with PCM in N3 dye calculation achieve the better approach regarding to experimental absorption spectra. The last two maximum absorption peaks dominated by charge transfer excitation are red shifted in ethanol solution with respect to the gas phase. Electronic polarization between complex and solvent caused the structure to relax, permitting a greater charge separation. IntroductionSince founded in 1990s, dye-sensitized solar cell (DSSC) has attracted many researchers' attention and the number of publication related to this research topic increasing quite rapidly in recent years. DSSC attracts many interests because this new kind of molecular solar cell achieved lower cost-efficiency ratio than the first and second generation solar cell, moreover, the development of DSSC still have wide area to be investigated in order to achieve higher efficiency while maintaining the low cost production [1]. Many research subtopics arises from DSSC investigation, such as finding new sensitizer, new semiconductor, new electrolyte system, electrolyte additives, controlling the semiconductor pore size, etc., both experimentally and computationally [2][3][4][5][6][7].DSSC is a solar cell that employed a dye (usually an organic or metal complex molecule) as a photon catcher, called sensitizer. DSSC provides an efficient source of renewable energy, environmentally friendly, and quite economical [8]. In the DSSC cells, the properties of components such as the sensitizer absorption spectra (UV-Vis spectra) [9] and redox properties [10] play an important role in the photovoltaic performance of DSSC cells. Solar energy absorbed by the sensitizer is used to inject electrons into the semiconductor photoanode then transferred to the conductor part. Hence, sensitizer material has a critical influence to the overall cell efficiency.One of the best sensitizerscomes from ruthenium polypyridyl complexes and its derivatives, such as N3 dye and black dye [11]. N3 dye is a famous name for dithiocyanatobis(2,2-bipyridine-4,4-

DFT and TD-DFT Investigation of a Charge Transfer Surface Resonance Raman Model of N3 Dye Bound to a Small TiO2 Nanoparticle

“…The peak for N3 at 300 nm is shifted to 320 nm in the N3 anion and 340 nm in the dianion; however, the peak in the visible at around 700 nm does not shift very much or vary systematically with charge. On the other hand, it is well known that theoretical simulations of Ru dyes, which include a solvent environment, give a much better representation of the experimental spectra [58,60,61]. In fact, if we simulate the spectrum of N3 in ethanol, as seen in Figure 9, we do find bands at 300, 378, 458, and 561 nm in the visible, which are much closer to experimental values.…”

“…Thus, we use the TD-DFT vacuum excitation calculations to analyze the nature of the excited states that are used for exciting time-dependent Raman spectra and to analyze the CT process. it is well known that theoretical simulations of Ru dyes, which include a solvent environment, give a much better representation of the experimental spectra [58,60,61]. In fact, if we simulate the spectrum of N3 in ethanol, as seen in Figure 9, we do find bands at 300, 378, 458, and 561 nm in the visible, which are much closer to experimental values.…”

Computational molecular design of NIR dyes with varying anchoring groups for improving the efficiency and stability of dye-sensitized solar cells

“…PCM solvent model using Ethanol solvent was also implemented during the theoretical MO calculations considering its suitability for reliable prediction of the HOMO energy as we have reported earlier. 28) Results of the MO calculation in terms of the optimized minimum energy structure along with the electron density distribution in the HOMO and LUMO of this dye is shown in Fig. 2.…”

“…26) Theoretical MO calculation for 3D structural optimization was done for the isolated molecule in the gaseous state as well as in the ethanol solution in the framework of the selfconsistent reaction field polarizable continuum model (PCM) 27) Previous theoretical investigations also emphasize that incorporation of solvent effects is necessary to describe the electronic absorption spectra more accurately. 28) In the theoretical calculations, judicious selection of a suitable basis set, theory and functional are required to make a logical balance between the computation cost and accuracy. In this work, 6-311G basis set was utilized with TD-DFT for electronic structure calculations.…”

A perspective on using experiment and theory to identify design principles in dye-sensitized solar cells

“…Excited state modelling of dyes in solution can be done using a polarizable continuum model (PCM) [13,14], but this model is not applicable to dyes adsorbed at surfaces. In the latter case the size of the system should be consistent with the computational resources available.…”