Electronic excitation and injection of Ru-N3 dye anchored to TiO2 surface

Abstract

A step-by-step theoretical protocol based on the density functional theory (DFT) and timedependent DFT (TD-DFT) has been performed to study a Ruthenium polypyridyl complex named cis-dithiocyanatobis-(4,4'-dicarboxy-2,2'-bipyridine)ruthenium(II) (N3) sensitized TiO2 solar cell including dye excitations and electronic injection. Three binding structures of N3 anchored to a TiO2 nanoparticle (TiO2)38 have been adopted. The electronic structures and optical properties of N3 dye in gas phase, in solutions (with the explicit and implicit solvent models), and interfaced with TiO2 have been calculated. The hybrid DFT exchange-correlation (XC) functional B3LYP and PBE0, the newly-modified PBE0 functional PBE0-1/3, and the long-range corrected DFT (LRC-DFT) XC functional Cam-B3LYP have been applied. It is found that both the DFT XC functionals and molecular environments play a crucial role on molecular properties, which affect both the spectral lineshapes and peak positions. Coupled with PCM model, TD-PBE0-1/3 produces the best result compared with the experimental spectrum of N3 in CH2Cl2, TD-B3LYP slightly underestimates the excitation energies, and TD-Cam-B3LYP overestimates the excitation energies of 0.4 − 0.5 eV. As the solvent polarity increases, the electronic absorption spectra of N3 dye blue shift. The absorption manners of N3 anchored to (TiO2)38 affect the electronic excitations, leading to different electronic injection pathways. Two of three anchoring manners favor the interfacial electronic transfer. In the end, three possible electronic injection pathways from the different parts of the excited dye to TiO2 nanoparticle have been suggested, indicating the different timescales of electron injections. I. INTRODUCTION To satisfy the currently increased global electricity needs, educe air pollution and cut global warming emissions, it is urgent to develop the practical and affordable renewable energy sources. Silicon solar cells have been commonly used for converting solar radiation to electricity. However, the complex manufacturing processes and high production costs involved limit their commercial application. Dye-sensitized solar cells (DSSCs) or Grätzel cells are an efficient type of thin-film photovoltaic cell. 1 They promise viable solutions to future large-scale solar-energy conversion issues on the basis of high efficiency and low cost, and have thus attracted considerable research activities involved to design and optimize DSSCs. DSSC technology arises from the concept of "artificial photosynthesis". In DSSCs, chlorophyll is replaced by a light absorbing dye. We know that the main components of a DSSC is a wide band gap semiconductor that is able to accept

Electron transport studies of dye-Sensitized solar cells based on natural sensitizer extracted from rengas (Gluta spp.) and mengkulang (Heritiera elata) wood

“…The most stable and high conversion efficiency have been achieved with ruthenium (Ru) polypyridal compounds, such as cis-dithiocyanobis(4,4'-di-carboxy-2,2'bipyridine) ruthenium(II) (N3), ditetrabutylammonium-cis-bis(isothiocyanato)bis(2,2'bipyridyl-4,4'-dicarboxylatol)ruthenium(II) (N719), and tris-tetrabutylammonium trithiocyanato-4,4',4"-tricarboxy-2,2:6',2"-terpyridineruthenium(II) (black dye) (Nazeeruddin et al 2001;Marwa et al 2016;Wang et al 2016). Although the conversion efficiency of ruthenium complex dyes is greater than 10%, there are some disadvantages that limit their potential.…”