Photoacoustic and Photocurrent Studies of Highly Porous TiO₂ Electrodes Sensitized by Quantum-Sized CdS

Photoacoustic (PA) and photocurrent (PC) spectra of highly porous TiO 2 have been measured. The PA spectrum shifts to the lower energy region and the PA intensity below the fundamental absorption edge of TiO 2 increases rapidly with an increase in the number of CdS coating layers to seven and becomes almost constant at more than seven layers. The increase in PC intensity and a clear shift of spectra to the lower energy region are observed with increasing number of CdS layers coated, indicating the possibility of the transfer of photoexcited electrons of CdS nanocrystals to the conduction band of TiO 2 .