Optical Properties of the Type-II Core-Shell TiO2@CdS Nanorods for Photovoltaic Applications

The well-known surface-functionalized method has been employed to synthesize TiO2@CdS core-shell nanorods using citric acid as a surface-functionalized agent. By varying the concentration of the citric acid, core-shell nanorods of core diameter 36 nm with different shell thickness (19-34 nm) were formed. The UV-visible absorption spectra of the core-shell nanorods show a red shift of the band edge of uncoated TiO2, and the broadening of the absorption spectra is also observed with shell growth. Steady-state photoluminescence (PL) spectra of the core-shell nanorods give a new emission in the visible region and also red shift with the increasing shell thickness. Decay kinetics indicate that the average lifetime <tau > of the core-shell nanorods is larger than that of the uncoated TiO2, and it varies from nanoseconds to picoseconds. The current-voltage (I-V) curves of the core-shell nanorods give a photocurrent density that is 212 times greater than the dark current density.