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

Fused Double Donor Design with a Cross-Conjugated Dibenzosilin for Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSCs) can provide a clean energy solution to growing energy demands. In order to have devices of high performance, sensitizers that are able to absorb in the near-infrared region (NIR) are needed. Stronger electron donors are needed for intramolecular charge-transfer sensitizers to access longer wavelength photons. Thus, two novel organic dyes with a cross-conjugated dibenzosilin double donor design are studied herein. The double donor delocalizes multiple filled orbitals across both amine donors due to the fused design that planarizes the donor as observed computationally, which improves intramolecular charge-transfer strength. The dyes are studied via density functional theory (DFT), optical spectroscopy, electrochemistry, and in DSC devices. The studies indicate that the dye design can reduce recombination losses, allowing for improved DSC device performances relative to a single arylamine donor. The reduction in recombination losses is attributed to the six alkyl chains that are incorporated into the donor, which offer good surface protection.

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).