**3. Zinc oxide**

Zinc oxide (ZnO) has been investigated for a long time as it is an amazing material with multiple functions. ZnO is a direct wide bandgap semiconductor material with piezoelectric and photoelectric properties. ZnO has a wide direct bandgap of 3.37 eV which is similar to GaN and a high exciton binding energy of 60 meV at room temperature. The wide bandgap gives good optical transparency to visible light which makes ZnO a suitable candidate for short wavelength photonic applications (UV and blue spectral range). ZnO has a non-central symmetric wurtzite structure, and the relevant hexagonal unit cell (*a* = 3.25 Å, *c* = 5.20 Å) packed O2− closely and stacked Zn2+ layers alternately along the *c*-axis direction. Due to the unique fascinating property in electronics, optics, photonics, and magnetics, ZnO provides an impact on applications in various areas, such as solar cells, supercapacitors, sensors, catalysis, light-emitting, actuators, and biomedical devices. ZnO has equal importance in relation to silicon-based 1D nanostructures in the field of 1D

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**Figure 1.**

*Methodologies for Achieving 1D ZnO Nanostructures Potential for Solar Cells*

nanostructures, and it has an increasing influence in developing nanotechnology. To date, various quasi-one-dimensional nanostructures of ZnO have been synthesized, i.e., nanowires, nanobelts, and nanotubes [45–47]. **Figure 1(a**–**c)** expresses the images of ZnO rods taken by SEM synthesized at pH 8. It indicates that the length

*(a–c) ZnO nanorod images taken by SEM synthesized at pH 8 (a) 10 k×, (b) 100 k×, and (c) 300 k×.*

*DOI: http://dx.doi.org/10.5772/intechopen.83618*
