Growth of nitrogen-doped rutile TiO2 nanorod arrays and their improved performance in all-solid-state solar cells

Abstract

In this study, nitrogen-doped rutile TiO2 nanorod arrays (N–TiO2) were prepared through a facile hydrothermal process for the first time, using ammonia and butyl titanate as nitrogen and titanium source, respectively. The crystal structure and morphology of N–TiO2 were investigated by x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), which showed that the length and diameter of the nanorods as well as the intensity of (0 0 2) diffraction peak increased sharply with doping concentration. According to the x-ray photoelectron spectroscopy (XPS), only a small amount of nitrogen in reactants was deposited on the surface of TiO2 nanorods, and even less could enter into bulk TiO2 and form O–Ti–N structure. With the increase of doped nitrogen content, photoelectrical conversion efficiency of all-solid-state dye-sensitized solar cells first increased and then decreased, with the highest value of 2.88%, which was much higher than that of un-doped samples (1.57%). The improvement of the solar cells could be mainly attributed to vertical growth of the nanorod caused by the addition of nitrogen. After sintering treatment, the growth of (1 0 1) crystal face further increased the photoelectrical conversion efficiency to about 3.86%. Meanwhile, commercial liquid iodic electrolyte was also chosen to fabricate solar cells for comparison, and an efficiency of 5.36% was reached.