Abstract:
Hydrothermally synthesized vertically aligned Zinc Oxide (ZnO) Nano rod array are widely used in
semiconductor device applications including LEDs, transducers, sensors and solar cells. It is an interesting
material for third and fourth generation solar cells due to its thin and aligned morphology which increases
the effective surface area and improve charge transport. The aspect ratio of the nanorods found to be a
critical parameter for most of the device application particularly towards solar cell applications.
In this work, we report a simple solution process method to control the aspect ratio of the nanorods
by a modified hydrothermal synthesis. ZnO nanorods were fabricated on a 100 nm ZnO thin film coated
glass substrate. The growth solutions were prepared by mixing 100 ml of 50 mM Zinc acetate
(Zn(CH3COO)2·2H2O) and 100 ml of 50 mM hexamethylenetetramine ((CH2)6N4) (HMT). Polyethylenimine
(PEI) with molecular weight of 600 was used as a controlling agent. Growth were carried out different
times. Resulting Nano rods were characterized using Scanning electron microscopy (SEM), X-ray diffraction
(XRD) and UV-vis spectroscopy (UV-vis). Resulting Nano rods exhibited vertical orientation and uniform
distribution on the substrate with a hexagonal cross section. XRD confirmed that these nanorods grown
with and without PEI show highly crystalline hexagonal wurtzite phase. We found that the aspect ratio of
the nanorods increased when PEI is added to the growth solution. The average diameter and length of ZnO
Nanorods were determined as 60 nm and 125 nm with and without PEI in to the growth solution. The
length of the Nanorods was determined as ≈1 μm to ≈5 μm with and without PEI respectively. The variation
of aspect ratio with and without PEI with growth time will be discussed in the presentation
