Hydrothermally grown of well-aligned ZnONRs: dependence of alignment ordering upon precursor concentration

The well-aligned Zinc Oxide Nanorods (ZnONRs) arrays was obtained through a hydrothermal process at various precursor concentrations (PC) under a growth temperature of 90 °C for an hour. The effect of PC (0.02, 0.03, 0.04, 0.05, and 0.06 M which is denoted as K0.01–K0.06) to the structural, optical, and morfology (diameter, height, slope, and density) of ZnONRs were studied by using X-ray diffraction, UV–Vis spectroscopy, and field emission scanning electron microscopy (FESEM). As-synthesized ZnONRs exhibit an uniform growth direction along the [002] orientations with average diameters in the range of 40–90 nm. These nanorods showed a strong optical absorption peak centering at 367 nm,which is equivalent to optical energy band gap of ZnO 3.37 eV, confirming the formation of ZnONRs. The morfology of ZnONRs in term of diameter, height, slope, and density increases with the PC. The highest density of approximately 182 number/µm⁻² with average slope of 6 degree (aligning percentage of 83 ± 12%) was obtained at the PC of K0.04. It is interesting to find that the dye sensitized solar cell utilizing the sample K0.04 showed five times increasing in the power conversion efficiency as compared to that of device utilizing K0.02 sample.