| Summary: | Considerable attentions have been drawn towards modulation of organic dyes with the goal of realizing effectual dye-sensitized solar cells using density functional theory (DFT). In this respect, a series of D–A1–A2 dyes containing 2-vinyl-5-(5-vinyl-2-thienyl) thiophene bridged with C=S group (A1), 2-Cyano-2-pyran-4-ylidene-acetic acid (A2) and tertiary aromatic amines as donor (D) were designed and theoretically investigated for dye-sensitized solar cells (DSSCs). These dyes were simulated using DFT and time-dependent density functional theory to calculate their electronic and optical properties, molecular reactivity indices, natural population analysis, maximum open circuit voltage (VOC) and light harvesting efficiency (LHE). The results showed that the position as well as number of fluorine atoms on Cyano-2-pyran-4-ylidene-acetic acid unit have effect on the electronic properties without necessary change the band gap energy of the dyes; therefore tuned/modulated molecular properties of the dyes. Also, dyes with donor unit containing N,N-diphenylaniline (DA-7) presented lowest band gap than those containing N-(2-pyridyl)pyridin-2-amine (DA-8) and carbazole (DA-9); thus N-phenyl-aniline unit is a better electron donor. Keywords: Photovoltaic cell, Electronic properties, D–A–A dye sensitizer, DFT
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