Organic Dyes Containing Carbazole as Donor and π-Linker: Optical, Electrochemical, and Photovoltaic Properties

Abstract

A series of new metal free organic dyes containing carbazole as donor and π-linker have been synthesized and characterized as effective sensitizers for dye sensitized solar cells (DSSCs). The carbazole functionalized at C-2 and C-7 served as electron-rich bridge. The donor property of the carbazole is substantially enhanced on introduction of tert-butyl groups at C-3 and C-6 positions and the oxidation propensity of the dyes increased on insertion of thiophene unit in the conjugation pathway. These structural modifications fine-tuned the optical and electrochemical properties of the dyes. Additionally, the presence of tert-butyl groups on the carbazole nucleus minimized the intermolecular interactions which benefited the performance of DSSCs. The dyes served as efficient sensitizers in DSSCs owing to their promising optical and electrochemical properties. The efficiency of DSSCs utilizing these dyes as sensitizers ranged from 4.22 to 6.04%. The tert-butyl groups were found to suppress the recombination of injected electrons which contributed to the increment in the photocurrent generation (JSC) and open circuit voltage (VOC). A dye with carbazole donor functionalized with tert-butyl groups and the conjugation bridge composed of 2,7-disubstituted carbazole and thiophene fragments exhibited higher VOC value. However, the best device efficiency was observed for a dye with unsubstituted carbazole donor and the π-linker featuring carbazole and bithiophene units due to the high photocurrent generation arising from the facile injection of photogenerated electrons into the conduction band of titanium dioxide (TiO2) facilitated by the low-lying LUMO.

Molecular engineering of carbazole-fluorene sensitizers for high open-circuit voltage DSSCs: Synthesis and performance comparison with iodine and cobalt electrolytes

“…cm -1 ) observed, as expected, for the three dyes confirm the beneficial effect of the fluorene core inserted into the π-conjugated bridge since the ε of JM1-JM3 is much higher than those of other carbazole-based dyes reported by us and others [6][7][8][9][10][20][21]. Due to the presence of the fluorene motif in the molecular backbone, JM1-JM3 are also strongly fluorescent dyes with an emission maximum at around 600 nm in dichloromethane (Fig.…”

In silico designing of power conversion efficient organic lead dyes for solar cells using todays innovative approaches to assure renewable energy for future

“…Here, two different techniques: (a) the standardization-based technique 45 and (b) the Euclidean distance approach 41 were used. A good number of dyes already exist from the TPA chemical class and successful modeling was already performed for phenothiazine 22 and carbazole 46,47 dyes. Therefore, we have concentrated on designing new dyes for the chemical class of tetrahydroquinoline, indoline and N,N′-dialkylaniline employing their respective QSPR models as those dyes are the least explored ones under DSSCs.…”

Carbazole-based compounds containing aldehyde and cyanoacetic acid: optical properties and applications in photopolymerization

“…Of particular note is that the amino groups in these molecules can be readily oxidized to form stable cations, which in turn enhances the ability to transport positive charges. [6][7][8] Cyanoacrylic acid is most widely employed as an electron accepting group, especially for its use in dye-sensitized solar cells to attach the organic dye to the surface of titania nanocrystals.…”