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

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).

Effect of the Spatial Configuration of Donors on the Photovoltaic Performance of Double D-π-A Organic Dyes.

Three double D-π-A sensitizers (A1, A3, and A5) containing different donors (triphenylamine, methoxy-modified triphenylamine, and cyclic thiourea-functionalized triphenylamine) are synthesized to investigate the role of different donors in dye-sensitized solar cells (DSSCs). Detailed investigations of the sensitizers reveal that the spatial characteristics of donor units have a considerable impact on the light-harvesting, electrochemistry, and photovoltaic properties. Benefiting from the strong shielding ability of alkyl chains in the donor to its branch chains as observed in density functional theory (DFT), the open-circuit voltage (VOC = 712.0 mV) of A5-based DSSC is higher than those of A1 and A3 by 90 and 78 mV, respectively. Therefore, the A5-based DSSC delivers a good efficiency of 8.54%, relying on its effective suppression of interfacial recombination. The results indicate that the judiciously tailored donor unit is an effective approach to optimize dye configurations to further improve power conversion efficiencies.