Organic Dyes Containing a Cyanovinyl Entity in the Spacer for Solar Cells Applications

Abstract

Series of dyes containing a cyanovinyl entity in the spacer have been developed and characterized. Dye-sensitized solar cells (DSSCs) using the dyes as the sensitizers exhibited good efficiencies ranging from 3.48−4.92%, which reached 45−70% with respect to that of an N719-based device fabricated under similar conditions. In general, better DSSC performances are observed with molecules having a shorter distance between the internal cyanovinyl entity and the amine donor. Computational analysis indicated that the cyanovinyl entity may behave as a charge trap, especially in the long molecules studied, where the cyanovinyl group is away from the electron-donating amine by two or more aromatic groups. A positive correlation is observed between the theoretically calculated product of oscillator strengths and the charge shift at the cyanoacrylic acid group and the measured short-circuit current in DSSCs. Therefore, it is likely that the charge-trapping in the cyanovinyl entity reduces the electronic interaction between the dye and the attached TiO2 and, therefore, compromises the DSSC performance.

A New Series of Quadrupolar Type Two‐Photon Absorption Chromophores Bearing 11, 12‐Dibutoxydibenzo[a,c]‐phenazine Bridged Amines; Their Applications in Two‐Photon Fluorescence Imaging and Two‐Photon Photodynamic Therapy

“…A similar trend was also observed in dipolar compounds containing an internal cyanovinyl unit that we reported recently. [21] Further elongation of the conjugated spacer between the thiophene and the peripheral arylamine leads to slightly hypsochromatic shift of the absorption band in 8 and 9. Compound 3 probably has greater charge separation in the excited state in view of its longest absorption and emission (vide infra) wavelengths among all these compounds.…”

Molecular Engineering and Theoretical Investigation of Novel Metal-Free Organic Chromophores for Dye-Sensitized Solar Cells

“…In most of the organic dyes the donor segment is typically an aromatic amine such as carbazole [10], phenothiazine [11], triphenylamine [12], phenoxazine [13], indoline [14] etc. It has been reported that the presence of electron accepting moieties such as diketeopyrrolopyrrole [15], benzotriazole [16], cyanovinyl [17], plays an active role of auxiliary acceptors and they serve as effective charge transporters between the donor and acceptor [18]. Typically, thiophene and its derivatives have been successfully utilized as p-conjugation bridges in the molecular design of organic dyes, due to their polarizability and overall stability [19].…”

Novel Organic Sensitizers Containing 2,6-Difunctionalized Anthracene Unit for Dye Sensitized Solar Cells

“…The absorption band below 400 nm exhibited vibronic characteristics of anthracenyl entity for all dyes except An-3. The vibronic pattern may be buried under the intense absorption band due to bis(fluorenyl)amino moiety [18]. The λ max value of the ICT band decreases in the order of An-3 > An-4 > An-1 ≈ An-2.…”

“…Meanwhile, intermolecular dye aggregation and recombination of conduction-band electrons with triiodide present in the electrolyte have to be suppressed. In recent years, we have been interested in push-pull type metal-free sensitizers using arylamine as the electron donor and 2-cyanoacrylic acid as the electron acceptor [13][14][15][16][17][18][19][20][21]. In continuation of our studies on sensitizers, we became interested in dyes containing fused aromatic segments in the spacer based on the following reasons: (1) the rigid segment has less reorganization energy and may facilitate electron transfer; (2) rigid segments with a planar skeleton may reduce steric congestion and allow more compact dye packing on the TiO 2 surface.…”