Effect of Extending the Conjugation of Dye Molecules on the Efficiency and Stability of Dye-Sensitized Solar Cells

Abstract

We designed and synthesized two organic dyes (A6 and A10) for dye-sensitized solar cells (DSSCs) by extending the molecular conjugation strategy. The sensitizer A10 was constructed by inserting ethene into our previously reported sensitizer AZ6. The sensitizer A6 was obtained by further substituting the hydrogen of ethene with another donor (D) and π-bridge-acceptor (π–A) segment. The UV–vis spectra and J–V curves showed that the dyes A10 and A6 could effectively facilitate the light-harvesting and photocurrent densities with respect to AZ6. Consequently, the A10-based DSSC achieved an enhanced efficiency (8.54%) with a high photocurrent (18.81 mA cm–2). Desorption experiments of dyes adsorbed on TiO2 showed that compared with the monoanchoring dyes AZ6 and A10, the dianchoring configuration effectively strengthened the affinity of dye A6 with the photoanode, making it more difficult to leach from the photoanode. The A6-based DSSC shows outstanding stability, and its overall efficiency could remain 98.0% of its initial value after 3000 h of aging time, exceeding that of its monoanalogue AZ6 (remained 78.3% after 3000 h).

Conventional and Back-Illuminated Cobalt- and Iodine-Mediated Dye-Sensitized Solar Cells for Artificial and Solar Light Conversion

“…The thickness and structure of the photoanode define the amount of adsorbed dye, light-harvesting, and photocurrent generation . The absorbed concentration of each dye vs photoanode thickness and combination of transparent and scattering layers was studied, following similar works previously reported. − …”

Synthesis and Characterization of a Metal-Free Organic Dye-Sensitizer for Solar Cell: An Advanced Organic Chemistry Research-Based Laboratory

“…The absorption spectrum of 4 shows two major bands at 300–400 nm and 400–550 nm appearing in the lower and higher energy regions, respectively (Figure ). The UV–vis absorption band at 300–400 nm is attributed to the π–π* transition of the aromatic backbone which normally produces a strong absorption peak around 400 nm in conjugated systems. ,− Also, the 400–550 nm visible absorption band is ascribed to the intramolecular charge-transfer (ICT) transition between the electron-donating unit, and the electron-withdrawing moiety (Figure ). ,,− The charge-transfer absorption behavior is observed in a molecular complex that exhibits two or more molecular chromophores where one unit has electron-donating properties, and the other functions as the acceptor group.…”

“…The UV–vis absorption band at 300–400 nm is attributed to the π–π* transition of the aromatic backbone which normally produces a strong absorption peak around 400 nm in conjugated systems. ,− Also, the 400–550 nm visible absorption band is ascribed to the intramolecular charge-transfer (ICT) transition between the electron-donating unit, and the electron-withdrawing moiety (Figure ). ,,− The charge-transfer absorption behavior is observed in a molecular complex that exhibits two or more molecular chromophores where one unit has electron-donating properties, and the other functions as the acceptor group. The appearance of the intramolecular charge-transfer (ICT) transition in the UV–vis spectrum of 4 , and its absence in the UV–vis spectrum of its precursor, compound 3 , further validates the synthesis of 4 as an organic dye-sensitizer molecule (Figure ).…”

“…The excited-state redox potentials of the dye molecule change upon photoexcitation. , Therefore, to determine the LUMO energy of the excited dye, the LUMO is calculated by subtracting the zeroth–zeroth energy ( E 0–0 ), estimated from the onset wavelength of the absorption and emission spectrum of 4 from E – E ox (Figure ). − The LUMO level of dye 4 is sufficiently more negative than the conduction band energy level ( E cb ) of TiO 2 (0.5 V vs NHE) to allow excited electrons to be efficiently injected into the TiO 2 electrode (Figure ).…”

Visible, Far-Red, and Near-Infrared Active Unsymmetrical Squaraine Dyes Based on Extended Conjugation within the Polymethine Framework for Dye-Sensitized Solar Cells

“…Enhancing the DSSC device J SC is an important parameter to enhance the device efficiency by maintaining the V oc. Besides panchromatic absorption − and cosensitization, ,, NIR-light absorption is highly needed to enhance the device J SC . , Sensitizers with extended π-conjugation (with π-spacer and electron-deficient acceptor units) have been found as an important strategy to harvest the photons in the far-red and NIR regions. − In general, by extending the conjugation between the π-framework for D-A, D-π- A dyes and outside the polymethine framework of squaraine dyes leads 15–20 nm redshift in the absorption profile . However, extending the conjugation within the polymethine framework in cyanine dyes exhibited 100 nm redshifted transition per −CC– bond extension .…”