Electronic properties' modulation of D-A-A via fluorination of 2-cyano-2-pyran-4-ylidene-acetic acid acceptor unit for efficient DSSCs: DFT-TDDFT approach

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-A(1)-A(2) dyes containing 2-vinyl-5-(5-vinyl-2-thienyl) thiophene bridged with C=S group (A(1)), 2-Cyano-2-pyran-4-ylidene-acetic acid (A(2)) 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 (V-OC) 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. (C) 2020 The Author(s). Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative.