Effective improvement of the photovoltaic performance of black dye sensitized quasi-solid-state solar cells

We demonstrate the use of black dye for light harvesting in quasi-solid-state dye-sensitized solar cells. To improve the device performance, we utilize a phenothiazine-based dye for the postadsorption into the black dye anchored TiO2 nanoparticle surface. On the ground of the incident photon-to-electron conversion efficiency spectrum alternation, it is observed that the phenothiazine-based dye is inserted into the interstitial sites of the pre-adsorbed black dye molecules. This type of dye loading can (1) increase the light absorption for higher photocurrent density of the cosensitized devices and (2) suppress the back charge transfer from the conduction band of TiO2 to the electrolyte. The electrochemical characterizations confirm this conclusion. Finally, the efficiency is increased to 8.0%, which is improved by 27% and 23% when compared with the individual dye-sensitized devices.