Direct growth of oriented ZnO nanotubes by self-selective etching at lower temperature for photo-electrochemical (PEC) solar cell application

This paper presents a systematic study of the transformation of ZnO nanorods into ZnO nanotubes via a simple seed mediated growth hydrothermal technique at lower temperature. The growth process was carried out at 90 degrees C for 8 h to obtain high density ZnO nanorods, followed by decreasing the temperature of growth solution resulting in ZnO nanotubes. High density ZnO nanotubes have successfully been synthesized and grown directly on FTO substrate via self-selective etching at lower temperature for 16 h at 50 degrees C. It was found that the morphology of ZnO nanorod arrays in term of grain size and length increases with the growth time. The XRD analysis reveals that increasing the growth time and decreasing the growth temperature to 50 C affect the crystallite size of ZnO nanostructure. The optical absorption varies with the growth time. These ZnO samples have been applied as photovoltaic materials in a photoelectrochemical cell of FTO/ZnO/electrolyte/platinum. The PEC utilizing the ZnO nantubes demonstrates the J(SC), V-OG, FF and eta of 0.39 mA cm(-2), 0.36 V, 0.34% and 0.050%, respectively. (C) 2014 Elsevier B.V. All rights reserved.