Effect of steam treatment on photocurrent and dye–titania interaction in dye-doped titania gel

Thin titania-gel films containing dispersed fluorescein or alizarin were prepared by the sol–gel method and treated with steam in order to promote crystal growth of the titania particles. The incident photon to current efficiency (IPCE) value and the quantum efficiency of the photocurrent generation increased with an increase in the steam-treatment duration of the fluorescein-doped films. The quantum efficiency was improved by 14 times after 12-h steam treatment. The growth and crystallization of the titania particles by the steam treatment improved their electric conductivity. On the other hand, the photocurrent only slightly changed and the crystal slightly grew by the steam treatment in the alizarin-doped films. Alizarin molecules prevented the crystal growth of the titania gel due to their strong interaction with Ti around them.