Modifying Titania Using the Molten-Salt-Assisted Self-Assembly Process for Cadmium Selenide-Quantum Dot-Sensitized Photoanodes.

Sensitizing titania with semiconducting quantum dots (QDs) is an important field for the development of third-generation photovoltaics. Many methods have been developed to effectively incorporate QDs over the surface of mesoporous titania, assembled from the 20-25 nm titania nanoparticles. Here, we introduce a molten-salt-assisted self-assembly (MASA) method to fabricate CdSe-modified mesoporous titania photoanodes. A mixture of ethanol, two surfactants (cetyltrimethylammonium bromide and 10-lauryl ether), silica (tetramethyl orthosilicate) or titania source (Ti(OCH), acid (HNO), and cadmium nitrate solution was infiltrated into the pores of mesoporous titania (assembled using Degussa 25, P25) and immediately calcined at 450 °C to obtain mesoporous cadmium oxide-silica-titania (meso-CdO-SiO-P25) or cadmium titanate-titania (meso-CdTiO-P25) films. The MASA process is a simple method to smoothly coat or fill the pores of titania with mesoporous CdO-SiO or CdTiO that can be reacted under an HSe atmosphere to convert cadmium species to CdSe at 100 °C. Etching of the silica films with a very dilute hydrogen fluoride solution produces mesoporous CdSe-titania (meso-CdSe-P25) electrodes. The method is flexible to adjust the CdSe/TiO mole ratio over a very broad range in the films. The films were characterized at every stage of the preparation to demonstrate the effectiveness of the method. The electrodes were also tested in a simple two-electrode solar cell to demonstrate the performance of the electrodes that have a power conversion efficiency of 3.35%.