Theoretical Study of theπ-Bridge Influence with Different Units of Thiophene and Thiazole in Coumarin Dye-Sensitized Solar Cells

Abstract

Eight coumarin derivative dyes were studied by varying theπ-bridge size with different thiophene and thiazole units for their potential use in dye-sensitized solar cells (DSSC). Geometry optimization, the energy levels and electron density of the Highest Occupied Molecular Orbital and the Lowest Unoccupied Molecular Orbital, and ultraviolet-visible absorption spectra were calculated by Density Functional Theory (DFT) and Time-Dependent-DFT. All molecular properties were analyzed to decide which dye was the most efficient. Furthermore, chemical reactivity parameters, such as chemical hardness, electrophilicity index, and electroaccepting power, were obtained and analyzed, whose values predicted the properties of the dyes in addition to the rest of the studied molecular properties. Our calculations allow us to qualitatively study dye molecules and choose the best for use in a DSSC. The effects ofπ-bridges based on thiophenes, thiazoles, and combinations of the two were reviewed; dyes with three units mainly of thiazole were chosen as the best photosensitizers for DSSC.

Thiophene‐Extended Nickel Thiazoledithiolene: π‐Extended Fused‐Ring Metal Dithiolenes with Stabilized Frontier Orbitals

“…Decreased molar absorptivity as the result of substituting thiophene with thiazole has been previously noted by other authors,, and computational studies have shown that the transition oscillator strength continues to decrease with each additional substitution by thiazole . This difference in absorptivity can also be seen in the parent heterocycles themselves.…”

DFT/TD‐DFT Studies of Metal‐Free N‐Annulated Perylene Based Organic Sensitizers for Dye‐Sensitized Solar Cells: Is Thiophene Spacer Essential for Improving the DSSC Performance?

“…Hara et al studied coumarin based dyes with 1, 2 or 3 thiophene moiety, and found that the dye with two thiophene moieties to be effective dye in terms of electron injection into the conduction band of TiO 2 . Soto‐Rojo et al studied the chemical hardness ( ς ) of the coumarin based dyes containing different size of thiophene (one to three) linker and found that ς to decrease with increase in number of thiophene units. Considering ς as the measure of the resistance to the intramolecular charge transfer (ICT), a lower ς is desired for dye molecules to do ICT effectively.…”

Exploring the relevance of thiophene rings as bridge unit in acceptor‐bridge‐donor dyes on self‐aggregation and performance in DSSCs

“…Compounds containing only thiophene ( 1 ) have attracted widespread interest because of their linear and nonlinear optical properties with potential applications in telecommunications, optical computing, optical signal processing and for applications as sensitizers for DSSC . Due to their high structural stability, controllable electrochemical behavior, good performance in hole transporting ability, most efficient organic sensitizers that have A ‐bridge‐ D structure contain a π conjugation bridge composed of thiophene units among others.…”

“…Regarding the type of bridges, nowadays it is common to study π‐conjugated systems as thiophene and its derivatives. The use of thiazole‐based groups has also achieved interesting conversion efficiencies in DSSCs, mainly due to the red shift of the maximum absorption wavelength and the improvement of intramolecular charge transfer. Soto et al and Hara et al studied the performance of dyes with up to three thiophene units as the π‐bridge.…”

“…Conversely, cyanoacrylic acid is a small electron acceptor with a strong electron withdrawing ability, which makes it one of the most famous anchoring group . Arakawa et al developed a family of A ‐bridge‐ D dyes using coumarin dyes as donors and cyanoacrylic acid as acceptor linked with vinylene, isophorone, or thienyl groups . By adding this acceptor into the design, the systems achieved wider absorption spectra and improved efficiencies.…”