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A series of systematically tailored aryl acyclic (biphenyl, dye 1 and 2), cyclic (phenanthrene, dye 3 and 4) and methyl-substituted (dye 5) imidazole derivatives were synthesized and characterized for application in dye-sensitized solar cells (DSSCs).

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A series of 2‐quinolinone‐based molecular systems with three different acceptor groups and N/O‐alkylated quinolinone compounds have been synthesised in an attempt to understand their optical properties. All the compounds were characterised by 1H NMR, 13C NMR and mass analysis. Absorption measurements revealed that charge‐transfer transition was observed by introducing electron‐withdrawing acceptor groups. Alkylation of 2‐quinolinone at the O‐position thwarts the charge‐transfer transitions, whereas N‐alkylation retains the charge‐transfer property. The presence of resonance zwitterionic forms in the unalkylated and N‐alkylated quinolinone compounds play an important role in charge‐transfer transition. The effects of solvents on the absorption and emission properties of these compounds were probed through Lippert Mataga and ET(30) correlation. The Stokes shifts of O‐alkylated compounds were larger than those of the unalkylated and N‐alkylated quinolinone compounds. The observed higher quantum yield and Stokes shift for these compounds will make them ideal fluorescent probes. Incorporation of acceptor groups and alkylation in the quinolinone moiety alters their energy levels. Good thermal stability was observed for both unalkylated and alkylated quinolinone compounds. The trends observed in the photophysical and electrochemical properties were supported by theoretical studies. The observed tunable optical properties, which were achieved through simple N‐ vs. O‐alkylation, results in large Stokes shifts and thermal stability, which means that the 2‐quinolinone‐based molecular systems are expected to emerge as potential candidates for photovoltaic and biological applications.

A systematic design and synthesis of three push-pull metal-free organic dyes employing N-alkylated diphenylamine (D1), carbazole (D2), and phenothiazine (D3) as donor moieties are presented in this paper. While, vinylbenzene, methoxybenzene, and cyanoacrylic acid were used as π-linker, auxiliary donor, and acceptor moieties, respectively for all three dyes. The study focusses on identifying the best donor among the three in terms of simple molecular design. TiO 2 -based dye-sensitized solar cells (DSSC) were fabricated with these dyes. Further, dyes and their deprotonated forms were investigated using density functional theory (DFT) and time-dependent DFT analyses to characterize their electronic and optical properties. The variation in power conversion efficiency (PCE) was observed owing to change in coplanarity from freely rotating diphenylamine, fused planar carbazole, and nonplanar phenothiazine. Cyclic voltammetry was performed on D1, D2, and D3 indicated that the substitution at C3 position is effective in stabilizing the radical cation formed upon exposure to light, thereby preventing it from dimerization and degradation. Results illustrated that the dye-containing carbazole as donor (D2d) delivered the best PCE, viz., 3.7%. This was further enhanced to 4.2% on addition of chenodeoxycholic acid as a coadsorbent.

Both carbazole and pyrene are electron-rich aromatic systems and are expected to be potential donors when used in push-pull dye architecture in the field of DSSC. Herein, two novel pyrene-carbazole...

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