Tailoring of energy levels in (2Z)-2-cyano-2-[2-[(E)-2-[2-[(E)-2-(p-tolyl)vinyl]thieno[3,2-b]thiophen-5-yl]vinyl]pyran-4-ylidene]acetic acid derivatives via conjugate bridge and fluorination of acceptor units for effective D–π–A dye-sensitized solar cells: DFT–TDDFT approach

• DOI: 10.1007/s11164-016-2735-0
• Publication Date: 2016-09-29T08:53:56Z
• Authors: Banjo Semire; Abel Kolawole Oye...; Olusegun Ayobami ...
• Keywords: 7. Clean energy; 01 natural sciences; 0104 chemical sciences

Density functional theory (DFT) was employed to investigate the role of fused thiophene and bridged thiophene π-linkers as well as acceptor unit fluorination in modifying the properties of dye sensitizers for dye-sensitized solar cells (DSSCs). A series of novel (2Z)-2-cyano-2-[2-[(E)-2-[2-[(E)-2-(p-tolyl)vinyl]thieno[3,2-b]thiophen-5-yl]vinyl]pyran-4-ylidene]acetic acid derivatives were simulated using DFT and time-dependent density functional theory to calculate their electronic and optical properties, population analysis, global reactivity index and light harvesting efficiency. The results showed that dyes with bridged thiophene π-linker have narrower energy bandgap (E g) and longer absorption wavelength (λ max) than those with fused thiophene π-linker. Also, fluorination of the acceptor unit of the dyes enhanced the electron accepting ability of 2-cyano-2-pyran-4-ylidene-acetic acid by lowering the lowest unoccupied molecular orbital (LUMO) energy, which leads to lower E g, lower chemical hardness (η), and longer wavelength. Therefore, incorporation of fluorine atoms at the acceptor unit makes the conduction-band potential more favorable, leading to effective charge separation and charge transfer between donor and acceptor.