Molecular design and performance of hydroxylpyridium sensitizers for dye-sensitized solar cells.

Four hydroxylpyridium organic dyes were synthesized and applied in dye-sensitized solar cells (DSSCs). Hydroxylpyridium was introduced as an electron acceptor in donor-π-conjugated bridge-acceptor (D-π-A) system. The traditional anchoring groups, such as the carboxyl group, were replaced by hydroxyl group. It was found that the existence of the hydroxylpyridium exhibits a large effect on the absorption spectra of dyes JH401-JH404. For JH series of dyes, hexylthiophene was employed as the π-conjugated bridge, and triphenylamine, phenothiazine, and their derivatives were used as the electron donor. The performances of the dyes with different structure were investigated by photophysical, photovoltaic, and electrochemical methods. When applied in the DSSCs, the sensitizer JH401 yields the best efficiency, 2.6% (Jsc = 6.35 mA/cm(2), Voc = 605 mV, FF = 67.6%) under 100 mW/cm(2) light illumination. Its maximum incident photon-to-current conversion efficiency (IPCE) is 80% at 440 nm light wavelength, which is the highest IPCE value achieved with hydroxyl group adsorbent organic dyes so far.