We have used electrochemical impedance to investigate the improvement in photovoltaic performance in aging of ionic liquid dye-sensitized solar cells using a high-absorption coefficient organic dye (2E)-2-cyano-3-(5-(5-((E)-2-(10-(2-ethylhexyl)-10H-phenothiazin-7-yl)vinyl)thiophen-2-yl)thiophen-2-yl)acrylic acid, which is in contrast to N719-based devices. It was found that the enhancement is due to reduced recombination of the photoexcited electrons. The decreased recombination plausibly originates from molecular re-orientation along with cation adsorption, with Fourier transform infrared spectra lending support to the former mechanism. After aging, the photovoltaic device using the organic dye outperforms the counterpart by the ruthenium complex dye and achieves an impressive efficiency of 5.6% under AM 1.5 100 mW/cm2 illumination. Copyright © 2011 John Wiley & Sons, Ltd.