Dip Coated ZnO Films for Transparent Window Applications

Abstract

ZnO is widely used as a functional material because it has a wide and direct band gap, large excitons binding energy, and excellent chemical and thermal stability. ZnO is a semiconductor material which is widely used as transparent electrodes in solar cells, chemical and gas sensors and light emitting diodes, due to its unique electrical and optical properties. Zinc oxide (ZnO) thin films were deposited on glass substrate by dip coating technique. The effects of sol aging time on the deposition of ZnO films were studied by using the field emission scanning electron microscopy (FE-SEM) and optical transmission techniques. Thin films of ZnO were prepared on glass substrate and annealed at 300 C, 350 C and 400 C. The increase in sol aging time resulted in a gradual improvement in crystallinity. Effect of sol aging on optical transparency is quite obvious through increased transmission with prolonged sol aging time. Interestingly, 72-168 h sol aging time was found to be optimal to achieve smooth surface morphology, good crystallinity and high optical transmittance which were attributed to an ideal stability of solution. The UV-Vis transmittance spectrum of synthesized sample suggests the optical band gap value of 3.2 eV. Dip coating technique create ZnO films with potential for application as transparent electrodes in optoelectronic devices such as solar cell.