Photosensitization of nanostructured TiO2 with WS2 quantum sheets

Porous, nanostructured sol gel TiO2 (100 nm) has been sensitized with WS2 quantum sheets (approximately 5 nm) with the help of chemical bath deposition. The absorber has been characterized with help of energy dispersive X-ray (EDX), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, and light absorption measurements. The photosensitization was confirmed via electrochemical measurements. The surface of TiO2 has been modified by a thin Al2O3 film, which significantly enhanced the photocurrent density to 0.4-0.7 mA/cm2. Moiré patterns suggest that the S-W-S layers of WS2 are not perfectly aligned in the direction of the c-axis, emphasizing the role of lateral electron transfer, which is also evidenced by surface passivation experiments. With WS2, a new, cheap, environmentally friendly, and stable absorber material for the sensitization of wide band gap nanomaterials has been introduced.