Photoelectrochemical performance of cadmium sulfide quantum dots modified titania nanotube arrays

Abstract The cadmium sulfide quantum dots modified titania nanotube arrays (CdS QDs/TiO 2 NTAs) were prepared through a sequential sonication-assisted chemical bath deposition (CBD) process. The morphology and microstructure of CdS QDs/TiO 2 NTAs were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectroscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy and UV–vis diffuse reflectance spectroscopy. The photoelectrochemical performance of CdS QDs/TiO 2 NTAs was investigated under solar light illumination. The affecting parameters were studied including the nanotube length of TiO 2 NTAs, CBD cycles of CdS QDs and the annealing treatment of CdS QDs/TiO 2 NTAs. CdS QDs synthesized through 8 CBD cycles could uniformly cover on the tube walls of TiO 2 NTAs to form unique CdS QDs/TiO 2 NTAs with an open pore mouth. The appropriate annealing treatment at 400 °C for 60 min in N 2 atmosphere could improve the crystallinity of CdS QDs, and accordingly enhance the photovoltaic properties of CdS QDs/TiO 2 NTAs. Significantly, the nanotube length was the predominant factor affecting photoelectrochemical performance of CdS QDs/TiO 2 NTAs. The unannealed CdS QDs/TiO 2 NTAs with an optimal nanotube length of 12 μm achieved a short-circuit photocurrent density of 4.37 mA cm − 2 , an open circuit photovoltage of 1.10 V and a top photoconversion efficiency of 3.56%. Comparatively, the annealed CdS QDs/TiO 2 NTAs with an optimal nanotube length of 4 μm achieved a short-circuit photocurrent density of 6.31 mA cm − 2 , an open circuit photovoltage of 1.23 V and a top photoconversion efficiency of 4.18%. The suitable modification of crystalline CdS QDs could well improve the photoelectrochemical performance of TiO 2 NTAs photoanode.